<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:cc081d59-9320-41ea-a8ad-8e61f774d791,g:90f02e55-6663-4c08-a66a-2a037f7d68f7-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://portillos.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSUNAUDITED" xlink:type="simple" xlink:href="ptlo-20220925.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETSUNAUDITED"/>
  <link:definitionLink xlink:role="http://portillos.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSUNAUDITED" xlink:type="extended" id="i22e888ac021a40e18b12b37529b6f1e3_CONDENSEDCONSOLIDATEDBALANCESHEETSUNAUDITED">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_3e4e6047-254a-4450-8b88-4cee482de580" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_22fffd4d-21a4-4cb9-bef2-4d2779e328bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3e4e6047-254a-4450-8b88-4cee482de580" xlink:to="loc_us-gaap_AssetsAbstract_22fffd4d-21a4-4cb9-bef2-4d2779e328bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_6047c9cb-2941-4a3c-b23f-b8eea564109f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_22fffd4d-21a4-4cb9-bef2-4d2779e328bd" xlink:to="loc_us-gaap_AssetsCurrentAbstract_6047c9cb-2941-4a3c-b23f-b8eea564109f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_a45fb461-365f-4319-a5e9-e547087bce90" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6047c9cb-2941-4a3c-b23f-b8eea564109f" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_a45fb461-365f-4319-a5e9-e547087bce90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_8f14d283-e4cc-4645-8f2c-ae86b7854919" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6047c9cb-2941-4a3c-b23f-b8eea564109f" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_8f14d283-e4cc-4645-8f2c-ae86b7854919" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_77212854-7378-4d99-ba46-f2bb6d55d489" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6047c9cb-2941-4a3c-b23f-b8eea564109f" xlink:to="loc_us-gaap_InventoryNet_77212854-7378-4d99-ba46-f2bb6d55d489" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrent_5a0c3c81-e883-4029-b2b1-8d3df28e9f70" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrepaidExpenseCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6047c9cb-2941-4a3c-b23f-b8eea564109f" xlink:to="loc_us-gaap_PrepaidExpenseCurrent_5a0c3c81-e883-4029-b2b1-8d3df28e9f70" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_e1be86f9-c7e3-4152-80af-e29de1c0f649" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_6047c9cb-2941-4a3c-b23f-b8eea564109f" xlink:to="loc_us-gaap_AssetsCurrent_e1be86f9-c7e3-4152-80af-e29de1c0f649" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_dbdc24f1-1cff-45e5-931c-e9c83807af4d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_22fffd4d-21a4-4cb9-bef2-4d2779e328bd" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_dbdc24f1-1cff-45e5-931c-e9c83807af4d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsAbstract_3566f6d9-15bd-402f-8aa9-25ba4e3e71ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_22fffd4d-21a4-4cb9-bef2-4d2779e328bd" xlink:to="loc_us-gaap_OtherAssetsAbstract_3566f6d9-15bd-402f-8aa9-25ba4e3e71ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_74d58a3d-9dff-47f8-b8db-4a2e520004b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_3566f6d9-15bd-402f-8aa9-25ba4e3e71ef" xlink:to="loc_us-gaap_Goodwill_74d58a3d-9dff-47f8-b8db-4a2e520004b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedTradeNames_a8e46f5c-c377-4b20-8251-b4b5f10f4a3b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IndefiniteLivedTradeNames"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_3566f6d9-15bd-402f-8aa9-25ba4e3e71ef" xlink:to="loc_us-gaap_IndefiniteLivedTradeNames_a8e46f5c-c377-4b20-8251-b4b5f10f4a3b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsNet_5fe31415-b8a4-4fbb-9c43-9a274ac1b9bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_3566f6d9-15bd-402f-8aa9-25ba4e3e71ef" xlink:to="loc_us-gaap_OtherIntangibleAssetsNet_5fe31415-b8a4-4fbb-9c43-9a274ac1b9bd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_7f8c260d-b7f3-4b1f-9349-1e5f9a921e14" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_3566f6d9-15bd-402f-8aa9-25ba4e3e71ef" xlink:to="loc_us-gaap_EquityMethodInvestments_7f8c260d-b7f3-4b1f-9349-1e5f9a921e14" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_3c802716-2b21-4cfd-96fb-cd98df45009d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_3566f6d9-15bd-402f-8aa9-25ba4e3e71ef" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_3c802716-2b21-4cfd-96fb-cd98df45009d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_2fd02979-f576-43e9-9738-4162212ee1d9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsMiscellaneousNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_3566f6d9-15bd-402f-8aa9-25ba4e3e71ef" xlink:to="loc_us-gaap_OtherAssetsMiscellaneousNoncurrent_2fd02979-f576-43e9-9738-4162212ee1d9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_d9ef5160-9c30-4903-85b2-2c88321ed434" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_3566f6d9-15bd-402f-8aa9-25ba4e3e71ef" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_d9ef5160-9c30-4903-85b2-2c88321ed434" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_114bfd65-a175-4164-bb50-5561b9135605" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_22fffd4d-21a4-4cb9-bef2-4d2779e328bd" xlink:to="loc_us-gaap_Assets_114bfd65-a175-4164-bb50-5561b9135605" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_61778024-23ec-4b9b-8380-52efbe79fa10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3e4e6047-254a-4450-8b88-4cee482de580" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_61778024-23ec-4b9b-8380-52efbe79fa10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_efee1048-261d-4690-9a9a-9d1cd99aa1af" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_61778024-23ec-4b9b-8380-52efbe79fa10" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_efee1048-261d-4690-9a9a-9d1cd99aa1af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_3429f958-e4d8-408a-a610-458b7f5c701e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_efee1048-261d-4690-9a9a-9d1cd99aa1af" xlink:to="loc_us-gaap_AccountsPayableCurrent_3429f958-e4d8-408a-a610-458b7f5c701e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_5f96404b-cf81-4860-824c-4fa60ae13304" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_efee1048-261d-4690-9a9a-9d1cd99aa1af" xlink:to="loc_us-gaap_LongTermDebtCurrent_5f96404b-cf81-4860-824c-4fa60ae13304" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_596dcd27-3bca-448d-a398-d0bca9b87012" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_efee1048-261d-4690-9a9a-9d1cd99aa1af" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_596dcd27-3bca-448d-a398-d0bca9b87012" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_44fc5ba7-d280-4a90-bbe4-c45580cfa157" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_efee1048-261d-4690-9a9a-9d1cd99aa1af" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_44fc5ba7-d280-4a90-bbe4-c45580cfa157" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_1a46c749-b8cd-4663-a195-c63c5a970152" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_efee1048-261d-4690-9a9a-9d1cd99aa1af" xlink:to="loc_us-gaap_LiabilitiesCurrent_1a46c749-b8cd-4663-a195-c63c5a970152" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrentAbstract_4313cb7e-0564-4d39-ad01-5b1383607402" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_61778024-23ec-4b9b-8380-52efbe79fa10" xlink:to="loc_us-gaap_LiabilitiesNoncurrentAbstract_4313cb7e-0564-4d39-ad01-5b1383607402" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_32e35415-b2db-4787-b35e-94a62f8a6ba2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_4313cb7e-0564-4d39-ad01-5b1383607402" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_32e35415-b2db-4787-b35e-94a62f8a6ba2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRentCreditNoncurrent_710ad479-b81e-4836-ace0-3b8f1c7be099" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredRentCreditNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_4313cb7e-0564-4d39-ad01-5b1383607402" xlink:to="loc_us-gaap_DeferredRentCreditNoncurrent_710ad479-b81e-4836-ace0-3b8f1c7be099" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TaxReceivableAgreementLiability_ecc9d6d9-70be-439a-a59b-bf784a94a2a7" xlink:href="ptlo-20220925.xsd#ptlo_TaxReceivableAgreementLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_4313cb7e-0564-4d39-ad01-5b1383607402" xlink:to="loc_ptlo_TaxReceivableAgreementLiability_ecc9d6d9-70be-439a-a59b-bf784a94a2a7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_6ee46f97-22b1-4c9d-820f-1ff7f773be16" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_4313cb7e-0564-4d39-ad01-5b1383607402" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_6ee46f97-22b1-4c9d-820f-1ff7f773be16" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrent_0709f977-3b35-4dd9-bf4e-7e528a3c8075" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract_4313cb7e-0564-4d39-ad01-5b1383607402" xlink:to="loc_us-gaap_LiabilitiesNoncurrent_0709f977-3b35-4dd9-bf4e-7e528a3c8075" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_e9ed5454-6e94-4ef8-af50-7ed3cd2d265c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_61778024-23ec-4b9b-8380-52efbe79fa10" xlink:to="loc_us-gaap_Liabilities_e9ed5454-6e94-4ef8-af50-7ed3cd2d265c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_e3fefbb2-6d17-4b85-990a-a754faecfeee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_61778024-23ec-4b9b-8380-52efbe79fa10" xlink:to="loc_us-gaap_CommitmentsAndContingencies_e3fefbb2-6d17-4b85-990a-a754faecfeee" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityAbstract_90fcf884-075a-49c6-b010-149558cbdced" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_61778024-23ec-4b9b-8380-52efbe79fa10" xlink:to="loc_us-gaap_EquityAbstract_90fcf884-075a-49c6-b010-149558cbdced" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_23ee1d62-075d-4797-b3ac-9cc88927ff37" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_90fcf884-075a-49c6-b010-149558cbdced" xlink:to="loc_us-gaap_PreferredStockValue_23ee1d62-075d-4797-b3ac-9cc88927ff37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_a72d34e9-29a9-477b-b827-1f0f9e565d1c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_90fcf884-075a-49c6-b010-149558cbdced" xlink:to="loc_us-gaap_CommonStockValue_a72d34e9-29a9-477b-b827-1f0f9e565d1c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_1ee9ab19-c43d-4df9-9941-5440319bbf97" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_90fcf884-075a-49c6-b010-149558cbdced" xlink:to="loc_us-gaap_AdditionalPaidInCapital_1ee9ab19-c43d-4df9-9941-5440319bbf97" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_a24fd108-55ce-40fc-b7f9-daac0ea97b55" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_90fcf884-075a-49c6-b010-149558cbdced" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_a24fd108-55ce-40fc-b7f9-daac0ea97b55" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_6f04c78b-d834-46db-b324-ded17b11dc17" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_90fcf884-075a-49c6-b010-149558cbdced" xlink:to="loc_us-gaap_StockholdersEquity_6f04c78b-d834-46db-b324-ded17b11dc17" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_18cbc8e6-01c2-4726-a92d-259cf963fc4a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_90fcf884-075a-49c6-b010-149558cbdced" xlink:to="loc_us-gaap_MinorityInterest_18cbc8e6-01c2-4726-a92d-259cf963fc4a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_b57bb01a-e7ab-48b4-99d6-03615981de34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityAbstract_90fcf884-075a-49c6-b010-149558cbdced" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_b57bb01a-e7ab-48b4-99d6-03615981de34" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_0d22cc30-b29b-48ab-b8e4-5696553327e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_61778024-23ec-4b9b-8380-52efbe79fa10" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_0d22cc30-b29b-48ab-b8e4-5696553327e2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_34873ee0-be68-4db0-9535-df619c99ca51" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_3e4e6047-254a-4450-8b88-4cee482de580" xlink:to="loc_us-gaap_StatementTable_34873ee0-be68-4db0-9535-df619c99ca51" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_fbdd6f6a-9965-4c30-b7e6-bae318c739d4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_34873ee0-be68-4db0-9535-df619c99ca51" xlink:to="loc_us-gaap_StatementClassOfStockAxis_fbdd6f6a-9965-4c30-b7e6-bae318c739d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_fbdd6f6a-9965-4c30-b7e6-bae318c739d4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_fbdd6f6a-9965-4c30-b7e6-bae318c739d4" xlink:to="loc_us-gaap_ClassOfStockDomain_fbdd6f6a-9965-4c30-b7e6-bae318c739d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_043870a3-6626-4572-a290-baff8bc2ad50" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_fbdd6f6a-9965-4c30-b7e6-bae318c739d4" xlink:to="loc_us-gaap_ClassOfStockDomain_043870a3-6626-4572-a290-baff8bc2ad50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_6d9a6024-5e10-432f-b98e-c32399848ea9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_043870a3-6626-4572-a290-baff8bc2ad50" xlink:to="loc_us-gaap_CommonClassAMember_6d9a6024-5e10-432f-b98e-c32399848ea9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_32e958a7-9ca7-4433-a41a-01d62a0e0724" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_043870a3-6626-4572-a290-baff8bc2ad50" xlink:to="loc_us-gaap_CommonClassBMember_32e958a7-9ca7-4433-a41a-01d62a0e0724" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSUNAUDITEDParenthetical" xlink:type="simple" xlink:href="ptlo-20220925.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETSUNAUDITEDParenthetical"/>
  <link:definitionLink xlink:role="http://portillos.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSUNAUDITEDParenthetical" xlink:type="extended" id="i5f16bf676a3b44bf83b89cbe67c292b6_CONDENSEDCONSOLIDATEDBALANCESHEETSUNAUDITEDParenthetical">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_2ebac98f-25e3-41d3-b0d7-52d66271c558" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_2ebac98f-25e3-41d3-b0d7-52d66271c558" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_ae4dd0a8-0144-45a6-8c46-63928ae2d167" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_ae4dd0a8-0144-45a6-8c46-63928ae2d167" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_67a92092-8c54-4a4e-8083-6f7f5e47aa23" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:to="loc_us-gaap_PreferredStockSharesIssued_67a92092-8c54-4a4e-8083-6f7f5e47aa23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_5808e23c-4dc8-4f2d-b276-639b312edde6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_5808e23c-4dc8-4f2d-b276-639b312edde6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_ca258c80-5eae-4ac2-9762-d7c335105645" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_ca258c80-5eae-4ac2-9762-d7c335105645" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_2a5925a6-17c4-44e4-ac68-e59bfc503f1f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_2a5925a6-17c4-44e4-ac68-e59bfc503f1f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_6bae37a9-4309-4e1a-90d2-0970a99f00db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:to="loc_us-gaap_CommonStockSharesIssued_6bae37a9-4309-4e1a-90d2-0970a99f00db" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_495c8c7d-959f-4dc1-b735-bc06e17e39b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_495c8c7d-959f-4dc1-b735-bc06e17e39b4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_6fd02739-48ff-4419-9914-901803bc08f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_209b1acb-9b8c-4fda-b610-65a8f19a9414" xlink:to="loc_us-gaap_StatementTable_6fd02739-48ff-4419-9914-901803bc08f4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_50da0d61-a1d1-4d79-9cd2-b90f1f6a6887" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_6fd02739-48ff-4419-9914-901803bc08f4" xlink:to="loc_us-gaap_StatementClassOfStockAxis_50da0d61-a1d1-4d79-9cd2-b90f1f6a6887" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_50da0d61-a1d1-4d79-9cd2-b90f1f6a6887_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_50da0d61-a1d1-4d79-9cd2-b90f1f6a6887" xlink:to="loc_us-gaap_ClassOfStockDomain_50da0d61-a1d1-4d79-9cd2-b90f1f6a6887_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_8f34714f-3796-4d62-9f8c-d0050708e48b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_50da0d61-a1d1-4d79-9cd2-b90f1f6a6887" xlink:to="loc_us-gaap_ClassOfStockDomain_8f34714f-3796-4d62-9f8c-d0050708e48b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_856c7b21-2dda-404e-aeb3-fd671379c4cd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_8f34714f-3796-4d62-9f8c-d0050708e48b" xlink:to="loc_us-gaap_CommonClassAMember_856c7b21-2dda-404e-aeb3-fd671379c4cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_0cdecf16-8875-4527-8a98-bc99d0394293" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_8f34714f-3796-4d62-9f8c-d0050708e48b" xlink:to="loc_us-gaap_CommonClassBMember_0cdecf16-8875-4527-8a98-bc99d0394293" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSANDMEMBERSEQUITYUNAUDITED" xlink:type="simple" xlink:href="ptlo-20220925.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSANDMEMBERSEQUITYUNAUDITED"/>
  <link:definitionLink xlink:role="http://portillos.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSANDMEMBERSEQUITYUNAUDITED" xlink:type="extended" id="i610149d767174a9aa1f08c5838408488_CONDENSEDCONSOLIDATEDSTATEMENTSOFSTOCKHOLDERSANDMEMBERSEQUITYUNAUDITED">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_6dab3f51-d4e2-4a8a-9a14-fc19f9762ac1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_eb258e95-edb2-4174-8794-b575f80a0eb6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInTemporaryEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6dab3f51-d4e2-4a8a-9a14-fc19f9762ac1" xlink:to="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_eb258e95-edb2-4174-8794-b575f80a0eb6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquitySharesOutstanding_be9de3b2-abcb-45dd-9d4e-020451bc3e31" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TemporaryEquitySharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_eb258e95-edb2-4174-8794-b575f80a0eb6" xlink:to="loc_us-gaap_TemporaryEquitySharesOutstanding_be9de3b2-abcb-45dd-9d4e-020451bc3e31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_e1e13914-7067-45ba-b2ad-ba1b4c1b520f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_eb258e95-edb2-4174-8794-b575f80a0eb6" xlink:to="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_e1e13914-7067-45ba-b2ad-ba1b4c1b520f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityAccretionToRedemptionValue_58aa5ae9-c800-4028-b5f9-bbdd9f703f60" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TemporaryEquityAccretionToRedemptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInTemporaryEquityRollForward_eb258e95-edb2-4174-8794-b575f80a0eb6" xlink:to="loc_us-gaap_TemporaryEquityAccretionToRedemptionValue_58aa5ae9-c800-4028-b5f9-bbdd9f703f60" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquitySharesOutstanding_8fbd7a73-79c7-4f92-9a22-5023024295e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TemporaryEquitySharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_47446d37-a98d-4d11-81f9-f555237d08cd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6dab3f51-d4e2-4a8a-9a14-fc19f9762ac1" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_c4d14e86-e7bf-493e-950f-2629e22df159" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_c4d14e86-e7bf-493e-950f-2629e22df159" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_16d4e8c0-9062-4616-883d-bd54fd936bee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_SharesOutstanding_16d4e8c0-9062-4616-883d-bd54fd936bee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_0569092a-c384-492a-8a35-2aed2f41b840" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_0569092a-c384-492a-8a35-2aed2f41b840" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_CommonStockSharesSubscribedButUnissuedRepaymentOfSubscriptionReceivable_8eb79336-ab62-40f8-a20a-b287b9ee1f91" xlink:href="ptlo-20220925.xsd#ptlo_CommonStockSharesSubscribedButUnissuedRepaymentOfSubscriptionReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_ptlo_CommonStockSharesSubscribedButUnissuedRepaymentOfSubscriptionReceivable_8eb79336-ab62-40f8-a20a-b287b9ee1f91" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_66d3310f-d110-4687-9e96-d651e1b788f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_66d3310f-d110-4687-9e96-d651e1b788f9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_db175f47-5180-45c6-b17c-82f391543b57" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_db175f47-5180-45c6-b17c-82f391543b57" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockAccretionOfRedemptionDiscount_148e29de-3458-4ee9-99d7-26ded152b40e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PreferredStockAccretionOfRedemptionDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_PreferredStockAccretionOfRedemptionDiscount_148e29de-3458-4ee9-99d7-26ded152b40e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_46cb0c90-01e7-4967-9f01-37ad5db0d955" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_46cb0c90-01e7-4967-9f01-37ad5db0d955" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_d274cb79-bf62-4366-85d8-57268c085b43" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_d274cb79-bf62-4366-85d8-57268c085b43" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_5844cc24-153f-442e-b527-3ef8377e18e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_5844cc24-153f-442e-b527-3ef8377e18e3" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodValue_36fda339-e9a6-4635-afaf-cd873e948eb9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodValue_36fda339-e9a6-4635-afaf-cd873e948eb9" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_NoncontrollingInterestInterestAdjustment_a812654e-dada-42cb-8adc-97da07e9f902" xlink:href="ptlo-20220925.xsd#ptlo_NoncontrollingInterestInterestAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_ptlo_NoncontrollingInterestInterestAdjustment_a812654e-dada-42cb-8adc-97da07e9f902" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_AdjustmentsToAdditionalPaidInCapitalDeferredTaxReceivableAgreementAdjustment_30b644a2-f273-477c-8db4-7d5a31cfd00c" xlink:href="ptlo-20220925.xsd#ptlo_AdjustmentsToAdditionalPaidInCapitalDeferredTaxReceivableAgreementAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f6606d74-84f2-4978-b50b-39ac1e61b96b" xlink:to="loc_ptlo_AdjustmentsToAdditionalPaidInCapitalDeferredTaxReceivableAgreementAdjustment_30b644a2-f273-477c-8db4-7d5a31cfd00c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_337357f6-71a8-4ea3-9669-52e0cc73c0ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_111868f2-e3b4-40d4-8bd0-92060e1cd0b4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_5c2a5ca3-f9f5-434f-af61-0c7f83b4426c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_6dab3f51-d4e2-4a8a-9a14-fc19f9762ac1" xlink:to="loc_us-gaap_StatementTable_5c2a5ca3-f9f5-434f-af61-0c7f83b4426c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_0bb92a2b-9da3-4159-ba29-56c6a2320a2f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5c2a5ca3-f9f5-434f-af61-0c7f83b4426c" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_0bb92a2b-9da3-4159-ba29-56c6a2320a2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_0bb92a2b-9da3-4159-ba29-56c6a2320a2f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_0bb92a2b-9da3-4159-ba29-56c6a2320a2f" xlink:to="loc_us-gaap_EquityComponentDomain_0bb92a2b-9da3-4159-ba29-56c6a2320a2f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ee60c41d-6213-4b5d-bc6c-ecd04f53e830" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_0bb92a2b-9da3-4159-ba29-56c6a2320a2f" xlink:to="loc_us-gaap_EquityComponentDomain_ee60c41d-6213-4b5d-bc6c-ecd04f53e830" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_MembersEquityMember_277e47a9-3c2a-4141-b169-310ae1907c6b" xlink:href="ptlo-20220925.xsd#ptlo_MembersEquityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ee60c41d-6213-4b5d-bc6c-ecd04f53e830" xlink:to="loc_ptlo_MembersEquityMember_277e47a9-3c2a-4141-b169-310ae1907c6b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_de49f6c9-9720-47b6-a8ba-244208c60fc7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ee60c41d-6213-4b5d-bc6c-ecd04f53e830" xlink:to="loc_us-gaap_CommonStockMember_de49f6c9-9720-47b6-a8ba-244208c60fc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_0e822704-8c1d-443c-b51a-2d3b82e78480" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ee60c41d-6213-4b5d-bc6c-ecd04f53e830" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_0e822704-8c1d-443c-b51a-2d3b82e78480" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_f7b21be5-5cad-4329-bcd9-ec7c98a654d0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ee60c41d-6213-4b5d-bc6c-ecd04f53e830" xlink:to="loc_us-gaap_RetainedEarningsMember_f7b21be5-5cad-4329-bcd9-ec7c98a654d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_22ed7968-024a-49df-b018-c00d28d827ee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ee60c41d-6213-4b5d-bc6c-ecd04f53e830" xlink:to="loc_us-gaap_NoncontrollingInterestMember_22ed7968-024a-49df-b018-c00d28d827ee" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_1b1b1ca0-0be9-41a6-b9e3-ecc5daa28138" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_5c2a5ca3-f9f5-434f-af61-0c7f83b4426c" xlink:to="loc_us-gaap_StatementClassOfStockAxis_1b1b1ca0-0be9-41a6-b9e3-ecc5daa28138" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_1b1b1ca0-0be9-41a6-b9e3-ecc5daa28138_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1b1b1ca0-0be9-41a6-b9e3-ecc5daa28138" xlink:to="loc_us-gaap_ClassOfStockDomain_1b1b1ca0-0be9-41a6-b9e3-ecc5daa28138_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_356196aa-f29b-4d36-b70d-4356d2ec477d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_1b1b1ca0-0be9-41a6-b9e3-ecc5daa28138" xlink:to="loc_us-gaap_ClassOfStockDomain_356196aa-f29b-4d36-b70d-4356d2ec477d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_b24c9510-ac63-4979-af8e-3b88ca8c8307" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_356196aa-f29b-4d36-b70d-4356d2ec477d" xlink:to="loc_us-gaap_CommonClassAMember_b24c9510-ac63-4979-af8e-3b88ca8c8307" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_cfafdc07-2768-4ad7-bfe7-939ce1e20355" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_356196aa-f29b-4d36-b70d-4356d2ec477d" xlink:to="loc_us-gaap_CommonClassBMember_cfafdc07-2768-4ad7-bfe7-939ce1e20355" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/DESCRIPTIONOFBUSINESSDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#DESCRIPTIONOFBUSINESSDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/DESCRIPTIONOFBUSINESSDetails" xlink:type="extended" id="i100671c1a643491eab53d81def8f52a3_DESCRIPTIONOFBUSINESSDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_NumberOfFoodProductionCommissaries_0a459f20-ab37-40f0-b6b2-a918a1842cad" xlink:href="ptlo-20220925.xsd#ptlo_NumberOfFoodProductionCommissaries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_ptlo_NumberOfFoodProductionCommissaries_0a459f20-ab37-40f0-b6b2-a918a1842cad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfRestaurants_cff36090-da1f-4cb2-99c1-74d65c3ea96e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NumberOfRestaurants"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_NumberOfRestaurants_cff36090-da1f-4cb2-99c1-74d65c3ea96e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_996eb49a-45c4-4f87-aea2-74acf6b22a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_996eb49a-45c4-4f87-aea2-74acf6b22a7a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_NumberOfNonTraditionalRestaurants_2bbbaaab-8c05-43f8-ad1d-a6888585809b" xlink:href="ptlo-20220925.xsd#ptlo_NumberOfNonTraditionalRestaurants"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_ptlo_NumberOfNonTraditionalRestaurants_2bbbaaab-8c05-43f8-ad1d-a6888585809b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_adfb8c4a-dd6b-4a27-afec-40f475471fd8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_adfb8c4a-dd6b-4a27-afec-40f475471fd8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_df9481df-c67b-4b49-b26f-676dc7e81deb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_df9481df-c67b-4b49-b26f-676dc7e81deb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_8e88ec94-6b0a-4fcc-a6ad-9d57f0ac8458" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_8e88ec94-6b0a-4fcc-a6ad-9d57f0ac8458" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfStockIssuanceCosts_77e9e587-d2a6-44dd-9194-78a3d6a123d7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsOfStockIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_PaymentsOfStockIssuanceCosts_77e9e587-d2a6-44dd-9194-78a3d6a123d7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_PaymentOfStockIssuanceCostsOfferingCosts_f86dc2dd-c19b-4f8a-b980-8a1713ab9387" xlink:href="ptlo-20220925.xsd#ptlo_PaymentOfStockIssuanceCostsOfferingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_ptlo_PaymentOfStockIssuanceCostsOfferingCosts_f86dc2dd-c19b-4f8a-b980-8a1713ab9387" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_NumberOfVotesPerShare_e40b421b-e9eb-4d36-b5e9-9f080bbb881f" xlink:href="ptlo-20220925.xsd#ptlo_NumberOfVotesPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_ptlo_NumberOfVotesPerShare_e40b421b-e9eb-4d36-b5e9-9f080bbb881f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfRedeemablePreferredStock_c58049b1-ccf6-478a-b0ab-aecec1edae75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsForRepurchaseOfRedeemablePreferredStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfRedeemablePreferredStock_c58049b1-ccf6-478a-b0ab-aecec1edae75" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_817f9177-a330-470a-90e5-5d4ddce8e224" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_817f9177-a330-470a-90e5-5d4ddce8e224" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_b61eaba4-cae1-4a01-8fb5-ec152fba7a04" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_b61eaba4-cae1-4a01-8fb5-ec152fba7a04" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TaxReceivableAgreementTaxPayablePercentOfTaxSavings_8cd27c0b-305e-4020-947d-8819d8807dde" xlink:href="ptlo-20220925.xsd#ptlo_TaxReceivableAgreementTaxPayablePercentOfTaxSavings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_ptlo_TaxReceivableAgreementTaxPayablePercentOfTaxSavings_8cd27c0b-305e-4020-947d-8819d8807dde" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TaxReceivableAgreementTaxSavingsRetainedPercent_e5855cf5-d620-41f7-b39c-fb2f9beab06a" xlink:href="ptlo-20220925.xsd#ptlo_TaxReceivableAgreementTaxSavingsRetainedPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_ptlo_TaxReceivableAgreementTaxSavingsRetainedPercent_e5855cf5-d620-41f7-b39c-fb2f9beab06a" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_3a2c24f8-a732-4a12-ac83-81166c355ce0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_3a2c24f8-a732-4a12-ac83-81166c355ce0" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_79335e7a-284b-46f4-901e-fdbf95a4e0aa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_79335e7a-284b-46f4-901e-fdbf95a4e0aa" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_54210771-da37-4a5d-865f-716be3b129b2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_54210771-da37-4a5d-865f-716be3b129b2" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_8c8a9dfd-90b7-4c3c-962c-632985f1aaa2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_8c8a9dfd-90b7-4c3c-962c-632985f1aaa2" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_fde2b0fe-163c-4801-b7c4-d369421c6c0b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_eb629067-07dc-4c1d-9324-0291021f8d87" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_fde2b0fe-163c-4801-b7c4-d369421c6c0b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6eed7087-abd9-469d-90d7-4f0a6f9bbcdb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_fde2b0fe-163c-4801-b7c4-d369421c6c0b" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6eed7087-abd9-469d-90d7-4f0a6f9bbcdb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_6eed7087-abd9-469d-90d7-4f0a6f9bbcdb_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6eed7087-abd9-469d-90d7-4f0a6f9bbcdb" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_6eed7087-abd9-469d-90d7-4f0a6f9bbcdb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_aae59102-edd3-4ca3-a682-3dea00977cfe" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_6eed7087-abd9-469d-90d7-4f0a6f9bbcdb" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_aae59102-edd3-4ca3-a682-3dea00977cfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_COChicagoLLCMember_327d72b3-f0ea-45fa-a72d-6dce9893a2c0" xlink:href="ptlo-20220925.xsd#ptlo_COChicagoLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_aae59102-edd3-4ca3-a682-3dea00977cfe" xlink:to="loc_ptlo_COChicagoLLCMember_327d72b3-f0ea-45fa-a72d-6dce9893a2c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_3b54fee2-b50a-42cb-bb7a-bd1ced3abf88" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_fde2b0fe-163c-4801-b7c4-d369421c6c0b" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_3b54fee2-b50a-42cb-bb7a-bd1ced3abf88" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_3b54fee2-b50a-42cb-bb7a-bd1ced3abf88_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_3b54fee2-b50a-42cb-bb7a-bd1ced3abf88" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_3b54fee2-b50a-42cb-bb7a-bd1ced3abf88_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_a7672881-09db-4b9e-bbce-e028c8b76184" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_3b54fee2-b50a-42cb-bb7a-bd1ced3abf88" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_a7672881-09db-4b9e-bbce-e028c8b76184" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IPOMember_d133629f-4eff-4088-8a20-d4030a920a9e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IPOMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_a7672881-09db-4b9e-bbce-e028c8b76184" xlink:to="loc_us-gaap_IPOMember_d133629f-4eff-4088-8a20-d4030a920a9e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OverAllotmentOptionMember_e63f901c-087c-471d-8fa2-58ab04de989c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OverAllotmentOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_a7672881-09db-4b9e-bbce-e028c8b76184" xlink:to="loc_us-gaap_OverAllotmentOptionMember_e63f901c-087c-471d-8fa2-58ab04de989c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_SecondaryOfferingMember_2c72f1cf-d7e1-44cd-96ff-741b9fef6ba5" xlink:href="ptlo-20220925.xsd#ptlo_SecondaryOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_a7672881-09db-4b9e-bbce-e028c8b76184" xlink:to="loc_ptlo_SecondaryOfferingMember_2c72f1cf-d7e1-44cd-96ff-741b9fef6ba5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_9d0b85bb-9492-4647-aeb7-72ec32924711" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_fde2b0fe-163c-4801-b7c4-d369421c6c0b" xlink:to="loc_us-gaap_StatementClassOfStockAxis_9d0b85bb-9492-4647-aeb7-72ec32924711" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_9d0b85bb-9492-4647-aeb7-72ec32924711_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_9d0b85bb-9492-4647-aeb7-72ec32924711" xlink:to="loc_us-gaap_ClassOfStockDomain_9d0b85bb-9492-4647-aeb7-72ec32924711_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_28c39b2c-b2ef-4c56-b177-a6c9a6d5d30d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_9d0b85bb-9492-4647-aeb7-72ec32924711" xlink:to="loc_us-gaap_ClassOfStockDomain_28c39b2c-b2ef-4c56-b177-a6c9a6d5d30d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_1e6f3947-84f3-44e9-8578-57e69611950f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_28c39b2c-b2ef-4c56-b177-a6c9a6d5d30d" xlink:to="loc_us-gaap_CommonClassAMember_1e6f3947-84f3-44e9-8578-57e69611950f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_LLCInterestsMember_b2b3238b-0f14-41a4-baa0-659ca93e1b5f" xlink:href="ptlo-20220925.xsd#ptlo_LLCInterestsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_28c39b2c-b2ef-4c56-b177-a6c9a6d5d30d" xlink:to="loc_ptlo_LLCInterestsMember_b2b3238b-0f14-41a4-baa0-659ca93e1b5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_80a154f5-3013-4ab2-ba5e-e839ed403d93" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_28c39b2c-b2ef-4c56-b177-a6c9a6d5d30d" xlink:to="loc_us-gaap_CommonClassBMember_80a154f5-3013-4ab2-ba5e-e839ed403d93" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_2c716582-bb14-4069-85e0-bd51eeb99970" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_fde2b0fe-163c-4801-b7c4-d369421c6c0b" xlink:to="loc_us-gaap_DebtInstrumentAxis_2c716582-bb14-4069-85e0-bd51eeb99970" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_2c716582-bb14-4069-85e0-bd51eeb99970_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_2c716582-bb14-4069-85e0-bd51eeb99970" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_2c716582-bb14-4069-85e0-bd51eeb99970_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_589c9a4c-8120-4b0f-ab3f-f4fc6c417b1a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_2c716582-bb14-4069-85e0-bd51eeb99970" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_589c9a4c-8120-4b0f-ab3f-f4fc6c417b1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_SecondLienTermB3LoansMember_b3aa39bf-644d-4396-acab-21c6547e7a14" xlink:href="ptlo-20220925.xsd#ptlo_SecondLienTermB3LoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_589c9a4c-8120-4b0f-ab3f-f4fc6c417b1a" xlink:to="loc_ptlo_SecondLienTermB3LoansMember_b3aa39bf-644d-4396-acab-21c6547e7a14" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_bffa1cb1-8c2f-40bf-ac80-148439aa5f11" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_fde2b0fe-163c-4801-b7c4-d369421c6c0b" xlink:to="loc_srt_OwnershipAxis_bffa1cb1-8c2f-40bf-ac80-148439aa5f11" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_bffa1cb1-8c2f-40bf-ac80-148439aa5f11_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_bffa1cb1-8c2f-40bf-ac80-148439aa5f11" xlink:to="loc_srt_OwnershipDomain_bffa1cb1-8c2f-40bf-ac80-148439aa5f11_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_04690c54-490a-40d2-8be3-3b9b7f41bc95" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_bffa1cb1-8c2f-40bf-ac80-148439aa5f11" xlink:to="loc_srt_OwnershipDomain_04690c54-490a-40d2-8be3-3b9b7f41bc95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_PortillosOpCoMember_7b2dad1c-0ce0-4819-801c-47b85f7c7d02" xlink:href="ptlo-20220925.xsd#ptlo_PortillosOpCoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_04690c54-490a-40d2-8be3-3b9b7f41bc95" xlink:to="loc_ptlo_PortillosOpCoMember_7b2dad1c-0ce0-4819-801c-47b85f7c7d02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_ec7984a9-0a6d-4ffa-b812-c5998168a66f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_fde2b0fe-163c-4801-b7c4-d369421c6c0b" xlink:to="loc_srt_CounterpartyNameAxis_ec7984a9-0a6d-4ffa-b812-c5998168a66f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_ec7984a9-0a6d-4ffa-b812-c5998168a66f_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_ec7984a9-0a6d-4ffa-b812-c5998168a66f" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_ec7984a9-0a6d-4ffa-b812-c5998168a66f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d9eba9bc-1ea5-4812-8525-a648d5f1abc8" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_ec7984a9-0a6d-4ffa-b812-c5998168a66f" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d9eba9bc-1ea5-4812-8525-a648d5f1abc8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_PreIPOLLCMembersMember_45305b5b-d3d8-453d-a73a-db5f893606cf" xlink:href="ptlo-20220925.xsd#ptlo_PreIPOLLCMembersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d9eba9bc-1ea5-4812-8525-a648d5f1abc8" xlink:to="loc_ptlo_PreIPOLLCMembersMember_45305b5b-d3d8-453d-a73a-db5f893606cf" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails" xlink:type="extended" id="i76d949b24ca844d68c914c38b1521376_SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_caee350d-bc40-4944-ab59-63910756cce3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_1b989b7d-48b7-4ac6-9d61-ae91023cb879" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_caee350d-bc40-4944-ab59-63910756cce3" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_1b989b7d-48b7-4ac6-9d61-ae91023cb879" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_d1aab7c5-e122-4f37-9910-dbe2107246b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_caee350d-bc40-4944-ab59-63910756cce3" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_d1aab7c5-e122-4f37-9910-dbe2107246b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_68b2da54-d58e-4018-922f-d3d1442047c9" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_d1aab7c5-e122-4f37-9910-dbe2107246b7" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_68b2da54-d58e-4018-922f-d3d1442047c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_68b2da54-d58e-4018-922f-d3d1442047c9_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_68b2da54-d58e-4018-922f-d3d1442047c9" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_68b2da54-d58e-4018-922f-d3d1442047c9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_8dc109d5-3f4d-4fe7-8ea9-86a893590239" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_68b2da54-d58e-4018-922f-d3d1442047c9" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_8dc109d5-3f4d-4fe7-8ea9-86a893590239" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_COChicagoLLCMember_fdbcb936-eefc-4716-950d-278f6d728bed" xlink:href="ptlo-20220925.xsd#ptlo_COChicagoLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_8dc109d5-3f4d-4fe7-8ea9-86a893590239" xlink:to="loc_ptlo_COChicagoLLCMember_fdbcb936-eefc-4716-950d-278f6d728bed" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/REVENUERECOGNITIONGiftCardLiabilityDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#REVENUERECOGNITIONGiftCardLiabilityDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/REVENUERECOGNITIONGiftCardLiabilityDetails" xlink:type="extended" id="if8764a343eaf46de86de9383329cd44e_REVENUERECOGNITIONGiftCardLiabilityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_a172c205-717e-41cc-b138-93d62fc24ae4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_215ea010-2ba6-4733-8aef-c55719480aca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_a172c205-717e-41cc-b138-93d62fc24ae4" xlink:to="loc_us-gaap_ContractWithCustomerLiability_215ea010-2ba6-4733-8aef-c55719480aca" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3291c3b8-5e23-419a-8da1-6728323a32af" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_a172c205-717e-41cc-b138-93d62fc24ae4" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3291c3b8-5e23-419a-8da1-6728323a32af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_dff2fda9-3e89-4d48-ac22-7dbb14f0decf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_a172c205-717e-41cc-b138-93d62fc24ae4" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_dff2fda9-3e89-4d48-ac22-7dbb14f0decf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_c59bae09-d987-49c3-9f54-548f67ef8779" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_dff2fda9-3e89-4d48-ac22-7dbb14f0decf" xlink:to="loc_srt_ProductOrServiceAxis_c59bae09-d987-49c3-9f54-548f67ef8779" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_c59bae09-d987-49c3-9f54-548f67ef8779_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_c59bae09-d987-49c3-9f54-548f67ef8779" xlink:to="loc_srt_ProductsAndServicesDomain_c59bae09-d987-49c3-9f54-548f67ef8779_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_efffd8bf-a7c5-4074-b705-b1590490a169" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_c59bae09-d987-49c3-9f54-548f67ef8779" xlink:to="loc_srt_ProductsAndServicesDomain_efffd8bf-a7c5-4074-b705-b1590490a169" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_GiftCardMember_c0af01f3-b12c-4da2-9629-b9cb27a322ad" xlink:href="ptlo-20220925.xsd#ptlo_GiftCardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_efffd8bf-a7c5-4074-b705-b1590490a169" xlink:to="loc_ptlo_GiftCardMember_c0af01f3-b12c-4da2-9629-b9cb27a322ad" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/PROPERTYEQUIPMENTNETDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#PROPERTYEQUIPMENTNETDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/PROPERTYEQUIPMENTNETDetails" xlink:type="extended" id="i213ca03df49846fc91ec13da0d5b68d1_PROPERTYEQUIPMENTNETDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_006d29d3-64f9-4a65-8e73-6b9fdd5ae08e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_d5e88c81-c3a2-4f64-b6f7-efb34b8d0517" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_006d29d3-64f9-4a65-8e73-6b9fdd5ae08e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_d5e88c81-c3a2-4f64-b6f7-efb34b8d0517" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_9fe13e8a-72cf-4a09-8863-1159d1fefce0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_006d29d3-64f9-4a65-8e73-6b9fdd5ae08e" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_9fe13e8a-72cf-4a09-8863-1159d1fefce0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_d9245777-0e1a-4d59-aead-e5c2f324bb67" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_006d29d3-64f9-4a65-8e73-6b9fdd5ae08e" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_d9245777-0e1a-4d59-aead-e5c2f324bb67" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_6c7fcfc3-e96e-4e35-be65-db4266e8bdb2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_006d29d3-64f9-4a65-8e73-6b9fdd5ae08e" xlink:to="loc_us-gaap_Depreciation_6c7fcfc3-e96e-4e35-be65-db4266e8bdb2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_58a3f02f-64d5-4d45-a37e-892da7b1765a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_006d29d3-64f9-4a65-8e73-6b9fdd5ae08e" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_58a3f02f-64d5-4d45-a37e-892da7b1765a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_32fced61-c0f7-4dcb-99d5-85cac004c963" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_58a3f02f-64d5-4d45-a37e-892da7b1765a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_32fced61-c0f7-4dcb-99d5-85cac004c963" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_32fced61-c0f7-4dcb-99d5-85cac004c963_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_32fced61-c0f7-4dcb-99d5-85cac004c963" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_32fced61-c0f7-4dcb-99d5-85cac004c963_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_94073692-04ca-4319-be3f-159ffb62dd83" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_32fced61-c0f7-4dcb-99d5-85cac004c963" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_94073692-04ca-4319-be3f-159ffb62dd83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandImprovementsMember_db617839-f393-4757-b773-b94592bc0119" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LandImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_94073692-04ca-4319-be3f-159ffb62dd83" xlink:to="loc_us-gaap_LandImprovementsMember_db617839-f393-4757-b773-b94592bc0119" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_25d2d91b-3865-4ca7-9c4d-4599b072a163" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_94073692-04ca-4319-be3f-159ffb62dd83" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_25d2d91b-3865-4ca7-9c4d-4599b072a163" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_911e2622-8d55-471f-ae13-3956f36599bd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_94073692-04ca-4319-be3f-159ffb62dd83" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_911e2622-8d55-471f-ae13-3956f36599bd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransportationEquipmentMember_55b7011c-027c-4ce1-9524-956cdc12375f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransportationEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_94073692-04ca-4319-be3f-159ffb62dd83" xlink:to="loc_us-gaap_TransportationEquipmentMember_55b7011c-027c-4ce1-9524-956cdc12375f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_43d9a53d-778d-4e50-93da-2bdc9302a6f1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_94073692-04ca-4319-be3f-159ffb62dd83" xlink:to="loc_us-gaap_ConstructionInProgressMember_43d9a53d-778d-4e50-93da-2bdc9302a6f1" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/GOODWILLINTANGIBLEASSETSSummaryofIntangibleAssetsNetDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#GOODWILLINTANGIBLEASSETSSummaryofIntangibleAssetsNetDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/GOODWILLINTANGIBLEASSETSSummaryofIntangibleAssetsNetDetails" xlink:type="extended" id="ic9f9354f0f3e4394a0d7e1cc21edb25c_GOODWILLINTANGIBLEASSETSSummaryofIntangibleAssetsNetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_1d17cbb2-bdf7-41f5-94de-decdc93a8e24" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_1eaa2c1d-280c-42b9-9de9-6544f7e1b79f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_1d17cbb2-bdf7-41f5-94de-decdc93a8e24" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_1eaa2c1d-280c-42b9-9de9-6544f7e1b79f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_3726872c-ecf0-4462-8070-7e8344e6dc3a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_1d17cbb2-bdf7-41f5-94de-decdc93a8e24" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_3726872c-ecf0-4462-8070-7e8344e6dc3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_addb5209-02ed-45a3-9a7e-cbd9d732818d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_1d17cbb2-bdf7-41f5-94de-decdc93a8e24" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_addb5209-02ed-45a3-9a7e-cbd9d732818d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_5997963b-9e83-49a6-a11a-02aa2b4c9a69" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_1d17cbb2-bdf7-41f5-94de-decdc93a8e24" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_5997963b-9e83-49a6-a11a-02aa2b4c9a69" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_483d1d7b-217e-4dec-a348-1d9876a2a8d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_1d17cbb2-bdf7-41f5-94de-decdc93a8e24" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_483d1d7b-217e-4dec-a348-1d9876a2a8d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_3c6d2f48-999c-4c92-aafd-0fcd08d54fd1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_96dfe79b-8857-4fa5-8ffe-a61f68703bc6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_1d17cbb2-bdf7-41f5-94de-decdc93a8e24" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_96dfe79b-8857-4fa5-8ffe-a61f68703bc6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_85fb6192-d54a-423f-9576-4a3eb877fd33" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_1d17cbb2-bdf7-41f5-94de-decdc93a8e24" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_85fb6192-d54a-423f-9576-4a3eb877fd33" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b13d4cc4-ac74-48b9-8cd5-eb3cb8fd712d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_85fb6192-d54a-423f-9576-4a3eb877fd33" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b13d4cc4-ac74-48b9-8cd5-eb3cb8fd712d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b13d4cc4-ac74-48b9-8cd5-eb3cb8fd712d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b13d4cc4-ac74-48b9-8cd5-eb3cb8fd712d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b13d4cc4-ac74-48b9-8cd5-eb3cb8fd712d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d3b6ea86-4b55-44f2-917f-06505091d59a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b13d4cc4-ac74-48b9-8cd5-eb3cb8fd712d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d3b6ea86-4b55-44f2-917f-06505091d59a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntellectualPropertyMember_e64bff6d-64c3-47f2-80bc-0618e44a757a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IntellectualPropertyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d3b6ea86-4b55-44f2-917f-06505091d59a" xlink:to="loc_us-gaap_IntellectualPropertyMember_e64bff6d-64c3-47f2-80bc-0618e44a757a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractBasedIntangibleAssetsMember_c9a04046-5c1b-46a7-b721-82b5f85d759d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d3b6ea86-4b55-44f2-917f-06505091d59a" xlink:to="loc_us-gaap_ContractBasedIntangibleAssetsMember_c9a04046-5c1b-46a7-b721-82b5f85d759d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#FAIRVALUEOFFINANCIALINSTRUMENTSDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/FAIRVALUEOFFINANCIALINSTRUMENTSDetails" xlink:type="extended" id="ie6a1a536515c4a7bab710d551407bb40_FAIRVALUEOFFINANCIALINSTRUMENTSDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_2cb99462-8a70-4a74-b8d7-1996d624dcc6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_f5882daa-efaf-4785-96fa-f6b0e8cf4251" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_2cb99462-8a70-4a74-b8d7-1996d624dcc6" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_f5882daa-efaf-4785-96fa-f6b0e8cf4251" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_41bd7187-ae2b-4b27-9327-69aa822a632f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_2cb99462-8a70-4a74-b8d7-1996d624dcc6" xlink:to="loc_us-gaap_AssetImpairmentCharges_41bd7187-ae2b-4b27-9327-69aa822a632f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_c34e57cd-a0a7-4aa7-94a0-caa1dd793dbd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_2cb99462-8a70-4a74-b8d7-1996d624dcc6" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_c34e57cd-a0a7-4aa7-94a0-caa1dd793dbd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_c7960748-c538-4a51-ad9b-751e54ccc534" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_c34e57cd-a0a7-4aa7-94a0-caa1dd793dbd" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_c7960748-c538-4a51-ad9b-751e54ccc534" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_c7960748-c538-4a51-ad9b-751e54ccc534_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_c7960748-c538-4a51-ad9b-751e54ccc534" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_c7960748-c538-4a51-ad9b-751e54ccc534_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_c98aa95f-8b6f-4762-8d94-8dc8b7cb4945" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_c7960748-c538-4a51-ad9b-751e54ccc534" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_c98aa95f-8b6f-4762-8d94-8dc8b7cb4945" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_815dc4d0-ace2-4b02-ad85-bb6788115fe8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_c98aa95f-8b6f-4762-8d94-8dc8b7cb4945" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_815dc4d0-ace2-4b02-ad85-bb6788115fe8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_48e0e6aa-afc2-4047-8988-3d4fc7bafb1a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_c34e57cd-a0a7-4aa7-94a0-caa1dd793dbd" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_48e0e6aa-afc2-4047-8988-3d4fc7bafb1a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_48e0e6aa-afc2-4047-8988-3d4fc7bafb1a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_48e0e6aa-afc2-4047-8988-3d4fc7bafb1a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_48e0e6aa-afc2-4047-8988-3d4fc7bafb1a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_32de7eb9-564b-4b7b-862c-3ef90db2da32" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_48e0e6aa-afc2-4047-8988-3d4fc7bafb1a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_32de7eb9-564b-4b7b-862c-3ef90db2da32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_899ebb82-1e28-4700-aaef-448884d4def6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_32de7eb9-564b-4b7b-862c-3ef90db2da32" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_899ebb82-1e28-4700-aaef-448884d4def6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_28100fd1-ef43-4c53-a568-fee6b22804fe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_c34e57cd-a0a7-4aa7-94a0-caa1dd793dbd" xlink:to="loc_us-gaap_FinancialInstrumentAxis_28100fd1-ef43-4c53-a568-fee6b22804fe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_28100fd1-ef43-4c53-a568-fee6b22804fe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_28100fd1-ef43-4c53-a568-fee6b22804fe" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_28100fd1-ef43-4c53-a568-fee6b22804fe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1e1dbe87-1b32-4d68-98b5-9caf1b91bf2e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_28100fd1-ef43-4c53-a568-fee6b22804fe" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1e1dbe87-1b32-4d68-98b5-9caf1b91bf2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_5a58fa92-122e-4d88-9bce-bc85d6d280fe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1e1dbe87-1b32-4d68-98b5-9caf1b91bf2e" xlink:to="loc_us-gaap_MoneyMarketFundsMember_5a58fa92-122e-4d88-9bce-bc85d6d280fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MutualFundMember_80d323d9-69af-48e0-ac7c-ccc74ce3e9e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MutualFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1e1dbe87-1b32-4d68-98b5-9caf1b91bf2e" xlink:to="loc_us-gaap_MutualFundMember_80d323d9-69af-48e0-ac7c-ccc74ce3e9e7" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/DEBTSummaryofDebtDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#DEBTSummaryofDebtDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/DEBTSummaryofDebtDetails" xlink:type="extended" id="i12bbf071667648b98217b7722e996f03_DEBTSummaryofDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_30e74964-f42f-4520-bf9d-6df70e5e5c28" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_667179b5-4b34-4a3e-882e-a15b4520e26b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_30e74964-f42f-4520-bf9d-6df70e5e5c28" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_667179b5-4b34-4a3e-882e-a15b4520e26b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_9de8c8dd-741b-49d3-9c08-ecce305580e4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_30e74964-f42f-4520-bf9d-6df70e5e5c28" xlink:to="loc_us-gaap_LineOfCredit_9de8c8dd-741b-49d3-9c08-ecce305580e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_35922576-c3e0-454c-9a46-e82372d38014" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_30e74964-f42f-4520-bf9d-6df70e5e5c28" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_35922576-c3e0-454c-9a46-e82372d38014" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_b1339e67-c415-476d-9eb3-3bd964380ec1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_30e74964-f42f-4520-bf9d-6df70e5e5c28" xlink:to="loc_us-gaap_LongTermDebt_b1339e67-c415-476d-9eb3-3bd964380ec1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_7717f36c-cd97-48d9-875e-c7b492e6a71d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_30e74964-f42f-4520-bf9d-6df70e5e5c28" xlink:to="loc_us-gaap_LongTermDebtCurrent_7717f36c-cd97-48d9-875e-c7b492e6a71d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_5a1f506d-980c-4a72-bf71-7a1fea751da5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_30e74964-f42f-4520-bf9d-6df70e5e5c28" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_5a1f506d-980c-4a72-bf71-7a1fea751da5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_1b7b6532-6733-44bf-9df6-78c8883de77f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_30e74964-f42f-4520-bf9d-6df70e5e5c28" xlink:to="loc_us-gaap_DebtInstrumentTable_1b7b6532-6733-44bf-9df6-78c8883de77f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_738b7f41-9e4c-4971-bba8-4d6efa813f2a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1b7b6532-6733-44bf-9df6-78c8883de77f" xlink:to="loc_us-gaap_DebtInstrumentAxis_738b7f41-9e4c-4971-bba8-4d6efa813f2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_738b7f41-9e4c-4971-bba8-4d6efa813f2a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_738b7f41-9e4c-4971-bba8-4d6efa813f2a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_738b7f41-9e4c-4971-bba8-4d6efa813f2a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1dda7cb8-7bba-4efb-8988-5e67f8d39cee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_738b7f41-9e4c-4971-bba8-4d6efa813f2a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1dda7cb8-7bba-4efb-8988-5e67f8d39cee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_FirstLienTermB3LoansMember_db637f39-46ea-4923-ab3f-0a39e21aabf6" xlink:href="ptlo-20220925.xsd#ptlo_FirstLienTermB3LoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_1dda7cb8-7bba-4efb-8988-5e67f8d39cee" xlink:to="loc_ptlo_FirstLienTermB3LoansMember_db637f39-46ea-4923-ab3f-0a39e21aabf6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_95a63241-797f-4476-941a-2dbfcfbad8dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1b7b6532-6733-44bf-9df6-78c8883de77f" xlink:to="loc_us-gaap_CreditFacilityAxis_95a63241-797f-4476-941a-2dbfcfbad8dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_95a63241-797f-4476-941a-2dbfcfbad8dd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_95a63241-797f-4476-941a-2dbfcfbad8dd" xlink:to="loc_us-gaap_CreditFacilityDomain_95a63241-797f-4476-941a-2dbfcfbad8dd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_e5144095-6061-4244-9506-0d065a9ba2a5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_95a63241-797f-4476-941a-2dbfcfbad8dd" xlink:to="loc_us-gaap_CreditFacilityDomain_e5144095-6061-4244-9506-0d065a9ba2a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_557557a2-144d-4939-be55-a39bec9180bf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_e5144095-6061-4244-9506-0d065a9ba2a5" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_557557a2-144d-4939-be55-a39bec9180bf" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/DEBTNarrativeDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#DEBTNarrativeDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/DEBTNarrativeDetails" xlink:type="extended" id="i0048ddef06cb47cba55f2517fa1c3b6a_DEBTNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_bfd4db75-281d-449c-a06a-499a7f3c80a7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_bfd4db75-281d-449c-a06a-499a7f3c80a7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_1da005f0-3d8a-454a-b7de-2735c89b16e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_1da005f0-3d8a-454a-b7de-2735c89b16e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_LineOfCreditFacilityAccordionFeatureIncreaseLimit_84a431f5-c2fe-427d-83ef-b1ad98a4f435" xlink:href="ptlo-20220925.xsd#ptlo_LineOfCreditFacilityAccordionFeatureIncreaseLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_ptlo_LineOfCreditFacilityAccordionFeatureIncreaseLimit_84a431f5-c2fe-427d-83ef-b1ad98a4f435" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_DebtInstrumentIncreaseDecreaseInBasisSpreadOnVariableRate_579860db-26b3-45c1-904a-dffec3f19778" xlink:href="ptlo-20220925.xsd#ptlo_DebtInstrumentIncreaseDecreaseInBasisSpreadOnVariableRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_ptlo_DebtInstrumentIncreaseDecreaseInBasisSpreadOnVariableRate_579860db-26b3-45c1-904a-dffec3f19778" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_8018100c-7405-4362-bc44-95286680ab10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_8018100c-7405-4362-bc44-95286680ab10" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_48a899d2-65bb-450d-a7b9-d9b0267beb93" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_48a899d2-65bb-450d-a7b9-d9b0267beb93" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentPeriodicPaymentPrincipal_c663c955-7b8c-4494-aaf3-8538dfcd0522" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentPeriodicPaymentPrincipal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_DebtInstrumentPeriodicPaymentPrincipal_c663c955-7b8c-4494-aaf3-8538dfcd0522" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_2934f458-cca6-4189-93ef-3d000a8fab0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_LineOfCredit_2934f458-cca6-4189-93ef-3d000a8fab0e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_f35e1d83-0f40-49b1-a755-2de19e50c273" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_f35e1d83-0f40-49b1-a755-2de19e50c273" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_LineOfCreditFacilityFrontingFeePercentage_3d323ac6-fed5-4957-9d17-dc573103a4a9" xlink:href="ptlo-20220925.xsd#ptlo_LineOfCreditFacilityFrontingFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_ptlo_LineOfCreditFacilityFrontingFeePercentage_3d323ac6-fed5-4957-9d17-dc573103a4a9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_ea4266c6-8ed4-4125-b874-784c028a1064" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_ea4266c6-8ed4-4125-b874-784c028a1064" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_86467635-6592-4a91-8b77-a2f43c50c486" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_86467635-6592-4a91-8b77-a2f43c50c486" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_a7c8cc36-cbd7-4bd7-b0cb-4b15a1ecbbed" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_a7c8cc36-cbd7-4bd7-b0cb-4b15a1ecbbed" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_46609709-4eac-41c7-8433-88f9c11b44ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_46609709-4eac-41c7-8433-88f9c11b44ce" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtExtinguishmentCosts_26efefe5-6dce-489a-bdf5-0ed12e6a63c8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsOfDebtExtinguishmentCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_PaymentsOfDebtExtinguishmentCosts_26efefe5-6dce-489a-bdf5-0ed12e6a63c8" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_7647d280-3a41-4419-acb9-606d4263db29" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_7647d280-3a41-4419-acb9-606d4263db29" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_5081e855-6a10-4c1b-956f-06cd367350b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_5081e855-6a10-4c1b-956f-06cd367350b9" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_352238dc-8ecc-4e0b-a3f8-cf818ba56b4e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_352238dc-8ecc-4e0b-a3f8-cf818ba56b4e" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_a8de7812-e7d0-410d-99e9-0b7aad2c24da" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_a8de7812-e7d0-410d-99e9-0b7aad2c24da" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_598fa3de-f47b-47b3-bf73-2d85c01a8ad5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_598fa3de-f47b-47b3-bf73-2d85c01a8ad5" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium_01272bba-d5d8-4412-abf0-e336ee7c0614" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AmortizationOfDebtDiscountPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_AmortizationOfDebtDiscountPremium_01272bba-d5d8-4412-abf0-e336ee7c0614" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_b9daa078-face-4fa8-a1f7-6e230c93c2d8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_InterestExpenseDebt_b9daa078-face-4fa8-a1f7-6e230c93c2d8" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_ce4f80fe-1b79-4814-a460-665aa5b193a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_08f09fbd-eca2-4cde-aece-979bcb0ebd66" xlink:to="loc_us-gaap_DebtInstrumentTable_ce4f80fe-1b79-4814-a460-665aa5b193a2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_bba52146-f4f2-45db-abd8-0a1513ff39df" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ce4f80fe-1b79-4814-a460-665aa5b193a2" xlink:to="loc_us-gaap_DebtInstrumentAxis_bba52146-f4f2-45db-abd8-0a1513ff39df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_bba52146-f4f2-45db-abd8-0a1513ff39df_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_bba52146-f4f2-45db-abd8-0a1513ff39df" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_bba52146-f4f2-45db-abd8-0a1513ff39df_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_f634c695-1922-45bf-a1f6-a592a7cf76dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_bba52146-f4f2-45db-abd8-0a1513ff39df" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_f634c695-1922-45bf-a1f6-a592a7cf76dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_FirstLienTermB3LoansMember_a3d575d4-23a5-48ee-a2be-6a957b1d0400" xlink:href="ptlo-20220925.xsd#ptlo_FirstLienTermB3LoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_f634c695-1922-45bf-a1f6-a592a7cf76dd" xlink:to="loc_ptlo_FirstLienTermB3LoansMember_a3d575d4-23a5-48ee-a2be-6a957b1d0400" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_SecondLienTermB3LoansMember_66117bf1-79d5-4c73-a13c-9cb58189c42a" xlink:href="ptlo-20220925.xsd#ptlo_SecondLienTermB3LoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_f634c695-1922-45bf-a1f6-a592a7cf76dd" xlink:to="loc_ptlo_SecondLienTermB3LoansMember_66117bf1-79d5-4c73-a13c-9cb58189c42a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_648ca4b1-e60c-457d-8978-d62111c6e8af" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ce4f80fe-1b79-4814-a460-665aa5b193a2" xlink:to="loc_us-gaap_CreditFacilityAxis_648ca4b1-e60c-457d-8978-d62111c6e8af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_648ca4b1-e60c-457d-8978-d62111c6e8af_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_648ca4b1-e60c-457d-8978-d62111c6e8af" xlink:to="loc_us-gaap_CreditFacilityDomain_648ca4b1-e60c-457d-8978-d62111c6e8af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_469425ae-169f-4c86-8d9f-9964237461cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_648ca4b1-e60c-457d-8978-d62111c6e8af" xlink:to="loc_us-gaap_CreditFacilityDomain_469425ae-169f-4c86-8d9f-9964237461cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_ce2384a5-e19c-4d0c-bb24-8377fc3bd4bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_469425ae-169f-4c86-8d9f-9964237461cc" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_ce2384a5-e19c-4d0c-bb24-8377fc3bd4bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_8c393c43-86ea-4df3-9102-9af9e269bf78" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_469425ae-169f-4c86-8d9f-9964237461cc" xlink:to="loc_us-gaap_LetterOfCreditMember_8c393c43-86ea-4df3-9102-9af9e269bf78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_2a52c0c0-756d-4631-8806-180b37658205" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ce4f80fe-1b79-4814-a460-665aa5b193a2" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_2a52c0c0-756d-4631-8806-180b37658205" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_2a52c0c0-756d-4631-8806-180b37658205_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2a52c0c0-756d-4631-8806-180b37658205" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_2a52c0c0-756d-4631-8806-180b37658205_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a218467f-ae36-4068-b55c-809cbdfe5551" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_2a52c0c0-756d-4631-8806-180b37658205" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a218467f-ae36-4068-b55c-809cbdfe5551" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TermLoanMember_33a6ce87-0294-4092-80ff-61731563d421" xlink:href="ptlo-20220925.xsd#ptlo_TermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a218467f-ae36-4068-b55c-809cbdfe5551" xlink:to="loc_ptlo_TermLoanMember_33a6ce87-0294-4092-80ff-61731563d421" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_ce2856ca-58a7-4a40-b136-8efb0745867e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ce4f80fe-1b79-4814-a460-665aa5b193a2" xlink:to="loc_us-gaap_VariableRateAxis_ce2856ca-58a7-4a40-b136-8efb0745867e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_ce2856ca-58a7-4a40-b136-8efb0745867e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_ce2856ca-58a7-4a40-b136-8efb0745867e" xlink:to="loc_us-gaap_VariableRateDomain_ce2856ca-58a7-4a40-b136-8efb0745867e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_d9af9333-753b-4e12-a8cf-5057169791f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_ce2856ca-58a7-4a40-b136-8efb0745867e" xlink:to="loc_us-gaap_VariableRateDomain_d9af9333-753b-4e12-a8cf-5057169791f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_770708e5-dbfd-4417-8b73-ca3f00ff68c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_d9af9333-753b-4e12-a8cf-5057169791f9" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_770708e5-dbfd-4417-8b73-ca3f00ff68c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_1d8a2127-0a78-4fa9-b198-855e07e91cf5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ce4f80fe-1b79-4814-a460-665aa5b193a2" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_1d8a2127-0a78-4fa9-b198-855e07e91cf5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1d8a2127-0a78-4fa9-b198-855e07e91cf5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1d8a2127-0a78-4fa9-b198-855e07e91cf5" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_1d8a2127-0a78-4fa9-b198-855e07e91cf5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_eee756d4-e336-4bc2-b146-5527f3bfdf66" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_1d8a2127-0a78-4fa9-b198-855e07e91cf5" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_eee756d4-e336-4bc2-b146-5527f3bfdf66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IPOMember_64a5b7a3-492b-47fa-90aa-2b39b4d8f2a2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IPOMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_eee756d4-e336-4bc2-b146-5527f3bfdf66" xlink:to="loc_us-gaap_IPOMember_64a5b7a3-492b-47fa-90aa-2b39b4d8f2a2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/NONCONTROLLINGINTERESTSNarrativeDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#NONCONTROLLINGINTERESTSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/NONCONTROLLINGINTERESTSNarrativeDetails" xlink:type="extended" id="ib0f914a974c843b4a9e166663963bb62_NONCONTROLLINGINTERESTSNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_2bca0bf7-244b-42d6-8d9a-a3743db4a21d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_f27158da-0e35-480f-a5fd-7c4825a73eea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_2bca0bf7-244b-42d6-8d9a-a3743db4a21d" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_f27158da-0e35-480f-a5fd-7c4825a73eea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_974cabf4-091c-4127-8fc7-1deab03c10ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_2bca0bf7-244b-42d6-8d9a-a3743db4a21d" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_974cabf4-091c-4127-8fc7-1deab03c10ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_NoncontrollingInterestWeightedAverageOwnershipPercentageByNoncontrollingOwners_0e5556fd-2bd2-41ab-b102-a5a8022542fc" xlink:href="ptlo-20220925.xsd#ptlo_NoncontrollingInterestWeightedAverageOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_2bca0bf7-244b-42d6-8d9a-a3743db4a21d" xlink:to="loc_ptlo_NoncontrollingInterestWeightedAverageOwnershipPercentageByNoncontrollingOwners_0e5556fd-2bd2-41ab-b102-a5a8022542fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_68a30211-fddc-4487-a6e1-51c789215757" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_2bca0bf7-244b-42d6-8d9a-a3743db4a21d" xlink:to="loc_us-gaap_MinorityInterestTable_68a30211-fddc-4487-a6e1-51c789215757" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_58ee32bd-e60e-419b-b9f9-6dd9e8334ade" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_68a30211-fddc-4487-a6e1-51c789215757" xlink:to="loc_us-gaap_StatementClassOfStockAxis_58ee32bd-e60e-419b-b9f9-6dd9e8334ade" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_58ee32bd-e60e-419b-b9f9-6dd9e8334ade_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_58ee32bd-e60e-419b-b9f9-6dd9e8334ade" xlink:to="loc_us-gaap_ClassOfStockDomain_58ee32bd-e60e-419b-b9f9-6dd9e8334ade_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_5f14509f-9d55-48d8-96c6-77e1409ea290" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_58ee32bd-e60e-419b-b9f9-6dd9e8334ade" xlink:to="loc_us-gaap_ClassOfStockDomain_5f14509f-9d55-48d8-96c6-77e1409ea290" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_260b5f27-2a51-44b1-9a63-6791c8bdb217" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_5f14509f-9d55-48d8-96c6-77e1409ea290" xlink:to="loc_us-gaap_CommonClassAMember_260b5f27-2a51-44b1-9a63-6791c8bdb217" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_LLCInterestsMember_ae41283e-c3e2-46dd-92fd-d9eac8d2e473" xlink:href="ptlo-20220925.xsd#ptlo_LLCInterestsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_5f14509f-9d55-48d8-96c6-77e1409ea290" xlink:to="loc_ptlo_LLCInterestsMember_ae41283e-c3e2-46dd-92fd-d9eac8d2e473" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_34094005-824b-45c3-86cc-10bdfe6de2d5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_68a30211-fddc-4487-a6e1-51c789215757" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_34094005-824b-45c3-86cc-10bdfe6de2d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_34094005-824b-45c3-86cc-10bdfe6de2d5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_34094005-824b-45c3-86cc-10bdfe6de2d5" xlink:to="loc_us-gaap_EquityComponentDomain_34094005-824b-45c3-86cc-10bdfe6de2d5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ce06b1b5-3f40-4ead-9496-2a020e0d48c4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_34094005-824b-45c3-86cc-10bdfe6de2d5" xlink:to="loc_us-gaap_EquityComponentDomain_ce06b1b5-3f40-4ead-9496-2a020e0d48c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_bc6b4cf6-eff5-4fee-80f0-7e41fe86f8fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ce06b1b5-3f40-4ead-9496-2a020e0d48c4" xlink:to="loc_us-gaap_CommonStockMember_bc6b4cf6-eff5-4fee-80f0-7e41fe86f8fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_99df146b-c779-4497-8b87-a0c0b3d49ac9" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_68a30211-fddc-4487-a6e1-51c789215757" xlink:to="loc_srt_OwnershipAxis_99df146b-c779-4497-8b87-a0c0b3d49ac9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_99df146b-c779-4497-8b87-a0c0b3d49ac9_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_99df146b-c779-4497-8b87-a0c0b3d49ac9" xlink:to="loc_srt_OwnershipDomain_99df146b-c779-4497-8b87-a0c0b3d49ac9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_c2d2992c-d903-497c-ba07-922acda667bb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_99df146b-c779-4497-8b87-a0c0b3d49ac9" xlink:to="loc_srt_OwnershipDomain_c2d2992c-d903-497c-ba07-922acda667bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_PortillosOpCoMember_a4a62718-00a5-40c2-9d57-913a1d50c4c9" xlink:href="ptlo-20220925.xsd#ptlo_PortillosOpCoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_c2d2992c-d903-497c-ba07-922acda667bb" xlink:to="loc_ptlo_PortillosOpCoMember_a4a62718-00a5-40c2-9d57-913a1d50c4c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_38df78ca-d449-4dbe-a259-d3f7ca38f154" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_68a30211-fddc-4487-a6e1-51c789215757" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_38df78ca-d449-4dbe-a259-d3f7ca38f154" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_38df78ca-d449-4dbe-a259-d3f7ca38f154_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_38df78ca-d449-4dbe-a259-d3f7ca38f154" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_38df78ca-d449-4dbe-a259-d3f7ca38f154_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_94828506-65c7-444a-82ae-c06c4be7acdc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_38df78ca-d449-4dbe-a259-d3f7ca38f154" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_94828506-65c7-444a-82ae-c06c4be7acdc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_SecondaryOfferingMember_8ffe5d61-e535-442e-80ee-682b7a048ab2" xlink:href="ptlo-20220925.xsd#ptlo_SecondaryOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_94828506-65c7-444a-82ae-c06c4be7acdc" xlink:to="loc_ptlo_SecondaryOfferingMember_8ffe5d61-e535-442e-80ee-682b7a048ab2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/NONCONTROLLINGINTERESTSScheduleofLLCinterestOwnershipbyPortillosIncandPreIPOLLCMembersDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#NONCONTROLLINGINTERESTSScheduleofLLCinterestOwnershipbyPortillosIncandPreIPOLLCMembersDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/NONCONTROLLINGINTERESTSScheduleofLLCinterestOwnershipbyPortillosIncandPreIPOLLCMembersDetails" xlink:type="extended" id="i2239d3519f5649fd97d8a80c066608be_NONCONTROLLINGINTERESTSScheduleofLLCinterestOwnershipbyPortillosIncandPreIPOLLCMembersDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_d47f3527-f902-4812-9474-7a5bf4256ddd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_264162c9-8eb7-4f8a-8547-b0b81c1418f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_d47f3527-f902-4812-9474-7a5bf4256ddd" xlink:to="loc_us-gaap_SharesOutstanding_264162c9-8eb7-4f8a-8547-b0b81c1418f4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_f23e6454-2319-484f-b6a1-45034b217896" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_d47f3527-f902-4812-9474-7a5bf4256ddd" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_f23e6454-2319-484f-b6a1-45034b217896" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_d67dfa1a-9082-4855-b25f-0e0f104a0eac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_d47f3527-f902-4812-9474-7a5bf4256ddd" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_d67dfa1a-9082-4855-b25f-0e0f104a0eac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_OwnershipPercentage_d2631bea-7e24-4d10-b697-0669faca6d59" xlink:href="ptlo-20220925.xsd#ptlo_OwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_d47f3527-f902-4812-9474-7a5bf4256ddd" xlink:to="loc_ptlo_OwnershipPercentage_d2631bea-7e24-4d10-b697-0669faca6d59" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_7f6510c1-4f3a-40a8-81ce-c678b3e1e860" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_d47f3527-f902-4812-9474-7a5bf4256ddd" xlink:to="loc_us-gaap_MinorityInterestTable_7f6510c1-4f3a-40a8-81ce-c678b3e1e860" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_f858b70a-2840-4f60-8ec3-7eaf977a996c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_7f6510c1-4f3a-40a8-81ce-c678b3e1e860" xlink:to="loc_us-gaap_StatementClassOfStockAxis_f858b70a-2840-4f60-8ec3-7eaf977a996c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_f858b70a-2840-4f60-8ec3-7eaf977a996c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f858b70a-2840-4f60-8ec3-7eaf977a996c" xlink:to="loc_us-gaap_ClassOfStockDomain_f858b70a-2840-4f60-8ec3-7eaf977a996c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_32b259a3-d154-4aaf-96c7-040e22792755" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_f858b70a-2840-4f60-8ec3-7eaf977a996c" xlink:to="loc_us-gaap_ClassOfStockDomain_32b259a3-d154-4aaf-96c7-040e22792755" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_91383ba6-2553-438f-9e78-6ca3a4e25f06" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_32b259a3-d154-4aaf-96c7-040e22792755" xlink:to="loc_us-gaap_CommonClassAMember_91383ba6-2553-438f-9e78-6ca3a4e25f06" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_b685628f-c377-415a-a3c8-b2ecfa53be27" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_32b259a3-d154-4aaf-96c7-040e22792755" xlink:to="loc_us-gaap_CommonClassBMember_b685628f-c377-415a-a3c8-b2ecfa53be27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_1a193859-7505-4c56-adc9-ceaf2bdd84f6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_7f6510c1-4f3a-40a8-81ce-c678b3e1e860" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_1a193859-7505-4c56-adc9-ceaf2bdd84f6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_1a193859-7505-4c56-adc9-ceaf2bdd84f6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_1a193859-7505-4c56-adc9-ceaf2bdd84f6" xlink:to="loc_us-gaap_EquityComponentDomain_1a193859-7505-4c56-adc9-ceaf2bdd84f6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_77ce7001-2553-4a5e-8e71-3048ebdcfcf4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_1a193859-7505-4c56-adc9-ceaf2bdd84f6" xlink:to="loc_us-gaap_EquityComponentDomain_77ce7001-2553-4a5e-8e71-3048ebdcfcf4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_8e023de6-5e28-41e8-a200-99d4db54ac8c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_77ce7001-2553-4a5e-8e71-3048ebdcfcf4" xlink:to="loc_us-gaap_CommonStockMember_8e023de6-5e28-41e8-a200-99d4db54ac8c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_0ab21a43-f62f-43ee-b775-b6f4b436612f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_7f6510c1-4f3a-40a8-81ce-c678b3e1e860" xlink:to="loc_srt_OwnershipAxis_0ab21a43-f62f-43ee-b775-b6f4b436612f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_0ab21a43-f62f-43ee-b775-b6f4b436612f_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_0ab21a43-f62f-43ee-b775-b6f4b436612f" xlink:to="loc_srt_OwnershipDomain_0ab21a43-f62f-43ee-b775-b6f4b436612f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_b2b169ff-7b8d-424d-b557-dc846854df10" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_0ab21a43-f62f-43ee-b775-b6f4b436612f" xlink:to="loc_srt_OwnershipDomain_b2b169ff-7b8d-424d-b557-dc846854df10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_PortillosOpCoMember_add91420-f990-4d27-933c-3685356e8291" xlink:href="ptlo-20220925.xsd#ptlo_PortillosOpCoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_b2b169ff-7b8d-424d-b557-dc846854df10" xlink:to="loc_ptlo_PortillosOpCoMember_add91420-f990-4d27-933c-3685356e8291" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/EQUITYBASEDCOMPENSATIONStockBasedCompensationExpenseDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#EQUITYBASEDCOMPENSATIONStockBasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/EQUITYBASEDCOMPENSATIONStockBasedCompensationExpenseDetails" xlink:type="extended" id="ia30c23e1cac646029b0850d55e947faf_EQUITYBASEDCOMPENSATIONStockBasedCompensationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3c07df32-8433-480e-897e-d0ea877f49a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_83f6c595-2558-420f-95f3-4cf1983be4fb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3c07df32-8433-480e-897e-d0ea877f49a6" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_83f6c595-2558-420f-95f3-4cf1983be4fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0f59d8fe-d2a2-4884-a53d-5613c3c78c84" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_3c07df32-8433-480e-897e-d0ea877f49a6" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0f59d8fe-d2a2-4884-a53d-5613c3c78c84" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_d8ed7f3b-ca58-4e1e-a5bf-e304d380220d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_0f59d8fe-d2a2-4884-a53d-5613c3c78c84" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_d8ed7f3b-ca58-4e1e-a5bf-e304d380220d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_d8ed7f3b-ca58-4e1e-a5bf-e304d380220d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_d8ed7f3b-ca58-4e1e-a5bf-e304d380220d" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_d8ed7f3b-ca58-4e1e-a5bf-e304d380220d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_ada772cc-e5c7-49fa-980e-f90e2d39439d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_d8ed7f3b-ca58-4e1e-a5bf-e304d380220d" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_ada772cc-e5c7-49fa-980e-f90e2d39439d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_LaborMember_f288cb03-4f6c-4f0d-a4b9-254e96ae5432" xlink:href="ptlo-20220925.xsd#ptlo_LaborMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_ada772cc-e5c7-49fa-980e-f90e2d39439d" xlink:to="loc_ptlo_LaborMember_f288cb03-4f6c-4f0d-a4b9-254e96ae5432" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_1952662a-fc71-492d-8d0d-cfa48a5a6d29" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_ada772cc-e5c7-49fa-980e-f90e2d39439d" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_1952662a-fc71-492d-8d0d-cfa48a5a6d29" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/EQUITYBASEDCOMPENSATIONNarrativeDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#EQUITYBASEDCOMPENSATIONNarrativeDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/EQUITYBASEDCOMPENSATIONNarrativeDetails" xlink:type="extended" id="i550fceba0e7f4b7bb21846de38e13799_EQUITYBASEDCOMPENSATIONNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_79e5d340-bb28-4e2c-8778-0ace684cd084" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_af51f4a0-d53b-4708-8f48-783b691885dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_79e5d340-bb28-4e2c-8778-0ace684cd084" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_af51f4a0-d53b-4708-8f48-783b691885dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_4677ec4a-67e9-4e54-8894-1d99626013fb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_79e5d340-bb28-4e2c-8778-0ace684cd084" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_4677ec4a-67e9-4e54-8894-1d99626013fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f142aab9-be02-4c8c-b84e-316f57416d95" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_79e5d340-bb28-4e2c-8778-0ace684cd084" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f142aab9-be02-4c8c-b84e-316f57416d95" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_cf9a6ae9-454e-4d8b-b636-ffcd1bb00476" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_f142aab9-be02-4c8c-b84e-316f57416d95" xlink:to="loc_us-gaap_AwardTypeAxis_cf9a6ae9-454e-4d8b-b636-ffcd1bb00476" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cf9a6ae9-454e-4d8b-b636-ffcd1bb00476_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_cf9a6ae9-454e-4d8b-b636-ffcd1bb00476" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cf9a6ae9-454e-4d8b-b636-ffcd1bb00476_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_43c71513-719d-433a-8ac6-168f51e0c429" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_cf9a6ae9-454e-4d8b-b636-ffcd1bb00476" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_43c71513-719d-433a-8ac6-168f51e0c429" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_a875dc23-32c7-4518-a21d-6162d8ad2fdc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_43c71513-719d-433a-8ac6-168f51e0c429" xlink:to="loc_us-gaap_EmployeeStockMember_a875dc23-32c7-4518-a21d-6162d8ad2fdc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/INCOMETAXESDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#INCOMETAXESDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/INCOMETAXESDetails" xlink:type="extended" id="i49cf3a4033154c1c8e29bd68cc970f96_INCOMETAXESDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyLineItems_1be8b47f-cfd1-44f7-acfc-ef21fa73bc85" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_1b7e64e2-ba9a-4a44-8a3c-92100ca9b546" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_1be8b47f-cfd1-44f7-acfc-ef21fa73bc85" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_1b7e64e2-ba9a-4a44-8a3c-92100ca9b546" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_8d27bf0b-438e-4185-87b1-352b9335d896" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_1be8b47f-cfd1-44f7-acfc-ef21fa73bc85" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_8d27bf0b-438e-4185-87b1-352b9335d896" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_DeferredTaxAssetsTaxReceivableAgreement_b9444707-127e-4d0a-955c-a03cca58a53b" xlink:href="ptlo-20220925.xsd#ptlo_DeferredTaxAssetsTaxReceivableAgreement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_1be8b47f-cfd1-44f7-acfc-ef21fa73bc85" xlink:to="loc_ptlo_DeferredTaxAssetsTaxReceivableAgreement_b9444707-127e-4d0a-955c-a03cca58a53b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TaxReceivableAgreementLiabilityIncreaseDecrease_348f1f57-adb7-4247-8099-aba640ad191f" xlink:href="ptlo-20220925.xsd#ptlo_TaxReceivableAgreementLiabilityIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_1be8b47f-cfd1-44f7-acfc-ef21fa73bc85" xlink:to="loc_ptlo_TaxReceivableAgreementLiabilityIncreaseDecrease_348f1f57-adb7-4247-8099-aba640ad191f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TaxReceivableAgreementLiability_eed942ce-cd07-444a-8af4-9d13ac0025c5" xlink:href="ptlo-20220925.xsd#ptlo_TaxReceivableAgreementLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_1be8b47f-cfd1-44f7-acfc-ef21fa73bc85" xlink:to="loc_ptlo_TaxReceivableAgreementLiability_eed942ce-cd07-444a-8af4-9d13ac0025c5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TaxReceivableAgreementAmountPaid_8a11ba1b-2726-4a45-bf3d-dd8be3d075a9" xlink:href="ptlo-20220925.xsd#ptlo_TaxReceivableAgreementAmountPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_1be8b47f-cfd1-44f7-acfc-ef21fa73bc85" xlink:to="loc_ptlo_TaxReceivableAgreementAmountPaid_8a11ba1b-2726-4a45-bf3d-dd8be3d075a9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyTable_3c2926b3-5a65-4c59-926c-b2d2b5e411b8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_1be8b47f-cfd1-44f7-acfc-ef21fa73bc85" xlink:to="loc_us-gaap_IncomeTaxContingencyTable_3c2926b3-5a65-4c59-926c-b2d2b5e411b8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_26139679-55b1-45f0-939d-84849f25d067" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_3c2926b3-5a65-4c59-926c-b2d2b5e411b8" xlink:to="loc_us-gaap_StatementClassOfStockAxis_26139679-55b1-45f0-939d-84849f25d067" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_26139679-55b1-45f0-939d-84849f25d067_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_26139679-55b1-45f0-939d-84849f25d067" xlink:to="loc_us-gaap_ClassOfStockDomain_26139679-55b1-45f0-939d-84849f25d067_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_9ebb8aaf-1676-4135-9cf5-673e7a582c16" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_26139679-55b1-45f0-939d-84849f25d067" xlink:to="loc_us-gaap_ClassOfStockDomain_9ebb8aaf-1676-4135-9cf5-673e7a582c16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_a1422210-0fa7-478d-b5c9-a4231fef426e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_9ebb8aaf-1676-4135-9cf5-673e7a582c16" xlink:to="loc_us-gaap_CommonClassAMember_a1422210-0fa7-478d-b5c9-a4231fef426e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_58313644-6aa0-416e-b3a6-d3a7f9b72747" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_3c2926b3-5a65-4c59-926c-b2d2b5e411b8" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_58313644-6aa0-416e-b3a6-d3a7f9b72747" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_58313644-6aa0-416e-b3a6-d3a7f9b72747_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_58313644-6aa0-416e-b3a6-d3a7f9b72747" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_58313644-6aa0-416e-b3a6-d3a7f9b72747_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_923ee754-f1fb-450f-8838-eb05587a75de" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_58313644-6aa0-416e-b3a6-d3a7f9b72747" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_923ee754-f1fb-450f-8838-eb05587a75de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_SecondaryOfferingMember_481b10ba-80e6-4da4-9cb9-08c64adf9a49" xlink:href="ptlo-20220925.xsd#ptlo_SecondaryOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_923ee754-f1fb-450f-8838-eb05587a75de" xlink:to="loc_ptlo_SecondaryOfferingMember_481b10ba-80e6-4da4-9cb9-08c64adf9a49" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/EARNINGSPERSHARENarrativeDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#EARNINGSPERSHARENarrativeDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/EARNINGSPERSHARENarrativeDetails" xlink:type="extended" id="i138ae2c380a44716a94d8097c250314f_EARNINGSPERSHARENarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_50c49ac7-cc86-495f-857f-646a89a31550" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_82fcc4ea-ae46-4a53-86b9-a9ae4a9541f7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_50c49ac7-cc86-495f-857f-646a89a31550" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_82fcc4ea-ae46-4a53-86b9-a9ae4a9541f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ae2aa9a2-1782-4867-aa9d-c50b5a8ae9b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_50c49ac7-cc86-495f-857f-646a89a31550" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ae2aa9a2-1782-4867-aa9d-c50b5a8ae9b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_bcc75e6c-7b43-4613-8dfe-641ab12e769d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_ae2aa9a2-1782-4867-aa9d-c50b5a8ae9b7" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_bcc75e6c-7b43-4613-8dfe-641ab12e769d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_bcc75e6c-7b43-4613-8dfe-641ab12e769d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_bcc75e6c-7b43-4613-8dfe-641ab12e769d" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_bcc75e6c-7b43-4613-8dfe-641ab12e769d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_efc3cc2a-8d1d-4d3a-8446-93135d664266" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_bcc75e6c-7b43-4613-8dfe-641ab12e769d" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_efc3cc2a-8d1d-4d3a-8446-93135d664266" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IPOMember_8f473f2b-4a04-4f5d-b465-5db2e88a207e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IPOMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_efc3cc2a-8d1d-4d3a-8446-93135d664266" xlink:to="loc_us-gaap_IPOMember_8f473f2b-4a04-4f5d-b465-5db2e88a207e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/EARNINGSPERSHAREScheduleofUnitsExcludedfromCalculationofDilutedEarningsperShareDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#EARNINGSPERSHAREScheduleofUnitsExcludedfromCalculationofDilutedEarningsperShareDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/EARNINGSPERSHAREScheduleofUnitsExcludedfromCalculationofDilutedEarningsperShareDetails" xlink:type="extended" id="i3baa909421d84f6784ece52bb5d0f754_EARNINGSPERSHAREScheduleofUnitsExcludedfromCalculationofDilutedEarningsperShareDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_367a5add-b3f7-4287-8877-d2c6f2e2c30d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_1cbf327f-69da-458c-9cdf-a2f7e358695d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_367a5add-b3f7-4287-8877-d2c6f2e2c30d" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_1cbf327f-69da-458c-9cdf-a2f7e358695d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_206efc17-6403-404c-9c70-21102e5ced44" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_367a5add-b3f7-4287-8877-d2c6f2e2c30d" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_206efc17-6403-404c-9c70-21102e5ced44" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_b279d692-c80a-4c4d-9da4-c7c4b72e16a8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_206efc17-6403-404c-9c70-21102e5ced44" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_b279d692-c80a-4c4d-9da4-c7c4b72e16a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b279d692-c80a-4c4d-9da4-c7c4b72e16a8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_b279d692-c80a-4c4d-9da4-c7c4b72e16a8" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_b279d692-c80a-4c4d-9da4-c7c4b72e16a8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_a5bb051a-3841-4b83-912d-2f60fccaeb2b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_b279d692-c80a-4c4d-9da4-c7c4b72e16a8" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_a5bb051a-3841-4b83-912d-2f60fccaeb2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_8709af99-b92d-4c6d-8782-cf75bd723d02" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_a5bb051a-3841-4b83-912d-2f60fccaeb2b" xlink:to="loc_us-gaap_PerformanceSharesMember_8709af99-b92d-4c6d-8782-cf75bd723d02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_AntidilutiveUnitsMember_e294f9fa-bf5e-476a-b0df-14a4f1007f60" xlink:href="ptlo-20220925.xsd#ptlo_AntidilutiveUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_a5bb051a-3841-4b83-912d-2f60fccaeb2b" xlink:to="loc_ptlo_AntidilutiveUnitsMember_e294f9fa-bf5e-476a-b0df-14a4f1007f60" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://portillos.com/role/RELATEDPARTYTRANSACTIONSDetails" xlink:type="simple" xlink:href="ptlo-20220925.xsd#RELATEDPARTYTRANSACTIONSDetails"/>
  <link:definitionLink xlink:role="http://portillos.com/role/RELATEDPARTYTRANSACTIONSDetails" xlink:type="extended" id="i24a906668b4e47a59870f635949a6c25_RELATEDPARTYTRANSACTIONSDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_8af7a29d-0cab-409c-bcbd-1eec594448ce" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableRelatedParties_5a3de0cb-0885-4e82-ada9-8ca74f7ffa02" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsReceivableRelatedParties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_8af7a29d-0cab-409c-bcbd-1eec594448ce" xlink:to="loc_us-gaap_AccountsReceivableRelatedParties_5a3de0cb-0885-4e82-ada9-8ca74f7ffa02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_81fd53c3-0e60-4503-94d6-3a7c5d4fefc4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_8af7a29d-0cab-409c-bcbd-1eec594448ce" xlink:to="loc_us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty_81fd53c3-0e60-4503-94d6-3a7c5d4fefc4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_5a4d2279-683e-4f8f-adb6-159c1be8a8d6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_8af7a29d-0cab-409c-bcbd-1eec594448ce" xlink:to="loc_us-gaap_AccountsPayableRelatedPartiesCurrentAndNoncurrent_5a4d2279-683e-4f8f-adb6-159c1be8a8d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TaxReceivableAgreementTaxPayablePercentOfTaxSavings_70810bcb-fe23-4589-8af3-8adb5fb7e332" xlink:href="ptlo-20220925.xsd#ptlo_TaxReceivableAgreementTaxPayablePercentOfTaxSavings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_8af7a29d-0cab-409c-bcbd-1eec594448ce" xlink:to="loc_ptlo_TaxReceivableAgreementTaxPayablePercentOfTaxSavings_70810bcb-fe23-4589-8af3-8adb5fb7e332" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TaxReceivableAgreementAmountPaid_74f18380-e440-4c2e-82ce-022d74e1cdaa" xlink:href="ptlo-20220925.xsd#ptlo_TaxReceivableAgreementAmountPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_8af7a29d-0cab-409c-bcbd-1eec594448ce" xlink:to="loc_ptlo_TaxReceivableAgreementAmountPaid_74f18380-e440-4c2e-82ce-022d74e1cdaa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_TaxReceivableAgreementLiability_de7f32e1-7d8a-4738-9b4d-0a3c2daccdda" xlink:href="ptlo-20220925.xsd#ptlo_TaxReceivableAgreementLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_8af7a29d-0cab-409c-bcbd-1eec594448ce" xlink:to="loc_ptlo_TaxReceivableAgreementLiability_de7f32e1-7d8a-4738-9b4d-0a3c2daccdda" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_38b90474-15cf-4e51-9e4f-045abd78c35b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_8af7a29d-0cab-409c-bcbd-1eec594448ce" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_38b90474-15cf-4e51-9e4f-045abd78c35b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_4632c51f-a22a-4117-997a-b8dd64c9b25e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_8af7a29d-0cab-409c-bcbd-1eec594448ce" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_4632c51f-a22a-4117-997a-b8dd64c9b25e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_c592b3c8-b686-4350-a5d8-d32b884d2c37" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_4632c51f-a22a-4117-997a-b8dd64c9b25e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_c592b3c8-b686-4350-a5d8-d32b884d2c37" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_c592b3c8-b686-4350-a5d8-d32b884d2c37_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_c592b3c8-b686-4350-a5d8-d32b884d2c37" xlink:to="loc_us-gaap_RelatedPartyDomain_c592b3c8-b686-4350-a5d8-d32b884d2c37_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_5266dc44-613e-4918-99ab-70d0e6afdde2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_c592b3c8-b686-4350-a5d8-d32b884d2c37" xlink:to="loc_us-gaap_RelatedPartyDomain_5266dc44-613e-4918-99ab-70d0e6afdde2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_7e9c7a6d-ce29-4aff-b130-c38e6373b03b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityMethodInvesteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_5266dc44-613e-4918-99ab-70d0e6afdde2" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_7e9c7a6d-ce29-4aff-b130-c38e6373b03b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_74380474-247b-4715-8c51-09733173f2ee" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_5266dc44-613e-4918-99ab-70d0e6afdde2" xlink:to="loc_srt_AffiliatedEntityMember_74380474-247b-4715-8c51-09733173f2ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_a9d3d1fc-7e11-4032-88c7-01122b8e3c13" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_4632c51f-a22a-4117-997a-b8dd64c9b25e" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_a9d3d1fc-7e11-4032-88c7-01122b8e3c13" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_a9d3d1fc-7e11-4032-88c7-01122b8e3c13_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_a9d3d1fc-7e11-4032-88c7-01122b8e3c13" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_a9d3d1fc-7e11-4032-88c7-01122b8e3c13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_6a93a175-d1cc-406c-bfc8-54a7aac5833c" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_a9d3d1fc-7e11-4032-88c7-01122b8e3c13" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_6a93a175-d1cc-406c-bfc8-54a7aac5833c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_COChicagoLLCMember_543db451-14c0-4c40-9835-17a196524e0d" xlink:href="ptlo-20220925.xsd#ptlo_COChicagoLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_6a93a175-d1cc-406c-bfc8-54a7aac5833c" xlink:to="loc_ptlo_COChicagoLLCMember_543db451-14c0-4c40-9835-17a196524e0d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_460faa41-5c4e-4f1e-935d-99c479ff59f2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_4632c51f-a22a-4117-997a-b8dd64c9b25e" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_460faa41-5c4e-4f1e-935d-99c479ff59f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_460faa41-5c4e-4f1e-935d-99c479ff59f2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_460faa41-5c4e-4f1e-935d-99c479ff59f2" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_460faa41-5c4e-4f1e-935d-99c479ff59f2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_067ee6f6-2320-4fac-928b-271069ad2708" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_460faa41-5c4e-4f1e-935d-99c479ff59f2" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_067ee6f6-2320-4fac-928b-271069ad2708" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_a2b14933-820b-43d9-9391-0e550c298635" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_067ee6f6-2320-4fac-928b-271069ad2708" xlink:to="loc_us-gaap_CostOfSalesMember_a2b14933-820b-43d9-9391-0e550c298635" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingIncomeExpenseMember_acf1443f-23a2-4a72-821b-4d137982e50a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherOperatingIncomeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_067ee6f6-2320-4fac-928b-271069ad2708" xlink:to="loc_us-gaap_OtherOperatingIncomeExpenseMember_acf1443f-23a2-4a72-821b-4d137982e50a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_3bc5446e-894a-4dbb-af6b-f879345330db" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_4632c51f-a22a-4117-997a-b8dd64c9b25e" xlink:to="loc_srt_OwnershipAxis_3bc5446e-894a-4dbb-af6b-f879345330db" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_3bc5446e-894a-4dbb-af6b-f879345330db_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_3bc5446e-894a-4dbb-af6b-f879345330db" xlink:to="loc_srt_OwnershipDomain_3bc5446e-894a-4dbb-af6b-f879345330db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_f1553045-6fdc-4a0f-be6f-200e73c137df" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_3bc5446e-894a-4dbb-af6b-f879345330db" xlink:to="loc_srt_OwnershipDomain_f1553045-6fdc-4a0f-be6f-200e73c137df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_PortillosOpCoMember_34f133af-2cdd-4e5d-88d5-fc8675b47d93" xlink:href="ptlo-20220925.xsd#ptlo_PortillosOpCoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_f1553045-6fdc-4a0f-be6f-200e73c137df" xlink:to="loc_ptlo_PortillosOpCoMember_34f133af-2cdd-4e5d-88d5-fc8675b47d93" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_PortillosIncMember_c360673c-d533-4cfc-bc15-8a1c0c06c513" xlink:href="ptlo-20220925.xsd#ptlo_PortillosIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_f1553045-6fdc-4a0f-be6f-200e73c137df" xlink:to="loc_ptlo_PortillosIncMember_c360673c-d533-4cfc-bc15-8a1c0c06c513" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_e5627245-7e06-40be-828b-a0315c5de869" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_4632c51f-a22a-4117-997a-b8dd64c9b25e" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_e5627245-7e06-40be-828b-a0315c5de869" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e5627245-7e06-40be-828b-a0315c5de869_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_e5627245-7e06-40be-828b-a0315c5de869" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_e5627245-7e06-40be-828b-a0315c5de869_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_07def3c8-8211-4944-afe2-ff8d5983d980" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_e5627245-7e06-40be-828b-a0315c5de869" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_07def3c8-8211-4944-afe2-ff8d5983d980" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_SecondaryOfferingMember_dcdf5b61-fae3-42cd-88c5-d0de88ec731d" xlink:href="ptlo-20220925.xsd#ptlo_SecondaryOfferingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_07def3c8-8211-4944-afe2-ff8d5983d980" xlink:to="loc_ptlo_SecondaryOfferingMember_dcdf5b61-fae3-42cd-88c5-d0de88ec731d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_66eb14e9-afab-4280-b090-e14f0b048cfc" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_4632c51f-a22a-4117-997a-b8dd64c9b25e" xlink:to="loc_dei_LegalEntityAxis_66eb14e9-afab-4280-b090-e14f0b048cfc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_66eb14e9-afab-4280-b090-e14f0b048cfc_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_66eb14e9-afab-4280-b090-e14f0b048cfc" xlink:to="loc_dei_EntityDomain_66eb14e9-afab-4280-b090-e14f0b048cfc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_2e08eab9-6ca7-40a4-8dc5-54d08a90cd6f" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_66eb14e9-afab-4280-b090-e14f0b048cfc" xlink:to="loc_dei_EntityDomain_2e08eab9-6ca7-40a4-8dc5-54d08a90cd6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ptlo_BerkshirePartnersLLCMember_81ddb3ab-2339-4d31-a999-07ead2b2e3e1" xlink:href="ptlo-20220925.xsd#ptlo_BerkshirePartnersLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_2e08eab9-6ca7-40a4-8dc5-54d08a90cd6f" xlink:to="loc_ptlo_BerkshirePartnersLLCMember_81ddb3ab-2339-4d31-a999-07ead2b2e3e1" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
