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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019ddb22-5e29-7729-b0a7-ea1e4d458fd8,g:a85dab38-e063-4a4e-95d2-4d6ec277b231-->
<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://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_MeganClarkenMember_019ddb22-5e29-7d3d-b882-f32920139056" xlink:href="crto-20260508.xsd#crto_MeganClarkenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_crto_MeganClarkenMember_019ddb22-5e29-7d3d-b882-f32920139056" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_MichaelKomasinskiMember_019ddb22-5e29-7580-9b27-8241a286be51" xlink:href="crto-20260508.xsd#crto_MichaelKomasinskiMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_crto_MichaelKomasinskiMember_019ddb22-5e29-7580-9b27-8241a286be51" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#PvpAdjustmentsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllAdjToCompMember" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#ecd_AllAdjToCompMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_ChangeInPensionValueAndAboveMarketNonQualifiedDeferredCompensationMember_019ddb22-5e29-77b2-a25d-a1a8a2381eca" xlink:href="crto-20260508.xsd#crto_ChangeInPensionValueAndAboveMarketNonQualifiedDeferredCompensationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_crto_ChangeInPensionValueAndAboveMarketNonQualifiedDeferredCompensationMember_019ddb22-5e29-77b2-a25d-a1a8a2381eca" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_GrantDateFairValueOfOptionAwardsAndStockAwardsGrantedInFiscalYearMember_019ddb22-5e29-7837-bc87-5d956d5a3540" xlink:href="crto-20260508.xsd#crto_GrantDateFairValueOfOptionAwardsAndStockAwardsGrantedInFiscalYearMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_crto_GrantDateFairValueOfOptionAwardsAndStockAwardsGrantedInFiscalYearMember_019ddb22-5e29-7837-bc87-5d956d5a3540" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_FairValueAtFiscalYearEndOfOutstandingAndUnvestedOptionAwardsAndStockAwardsGrantedInFiscalYearMember_019ddb22-5e29-735a-980d-8de3c81922a0" xlink:href="crto-20260508.xsd#crto_FairValueAtFiscalYearEndOfOutstandingAndUnvestedOptionAwardsAndStockAwardsGrantedInFiscalYearMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_crto_FairValueAtFiscalYearEndOfOutstandingAndUnvestedOptionAwardsAndStockAwardsGrantedInFiscalYearMember_019ddb22-5e29-735a-980d-8de3c81922a0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_ChangeInFairValueOfOutstandingAndUnvestedOptionAwardsAndStockAwardsGrantedInPriorFiscalYearsMember_019ddb22-5e29-7b3b-8a53-2f6296bca3d5" xlink:href="crto-20260508.xsd#crto_ChangeInFairValueOfOutstandingAndUnvestedOptionAwardsAndStockAwardsGrantedInPriorFiscalYearsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_crto_ChangeInFairValueOfOutstandingAndUnvestedOptionAwardsAndStockAwardsGrantedInPriorFiscalYearsMember_019ddb22-5e29-7b3b-8a53-2f6296bca3d5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_FairValueAtVestingOfOptionAwardsAndStockAwardsGrantedInFiscalYearThatVestedDuringFiscalYearMember_019ddb22-5e29-7d93-9bb4-930f63954044" xlink:href="crto-20260508.xsd#crto_FairValueAtVestingOfOptionAwardsAndStockAwardsGrantedInFiscalYearThatVestedDuringFiscalYearMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_crto_FairValueAtVestingOfOptionAwardsAndStockAwardsGrantedInFiscalYearThatVestedDuringFiscalYearMember_019ddb22-5e29-7d93-9bb4-930f63954044" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_ChangeInFairValueAsOfVestingDateOfOptionAwardsAndStockAwardsGrantedInPriorFiscalYearsForWhichApplicableVestingConditionsWereSatisfiedDuringFiscalYearMember_019ddb22-5e29-7a15-9a24-d16bf3a8c181" xlink:href="crto-20260508.xsd#crto_ChangeInFairValueAsOfVestingDateOfOptionAwardsAndStockAwardsGrantedInPriorFiscalYearsForWhichApplicableVestingConditionsWereSatisfiedDuringFiscalYearMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_crto_ChangeInFairValueAsOfVestingDateOfOptionAwardsAndStockAwardsGrantedInPriorFiscalYearsForWhichApplicableVestingConditionsWereSatisfiedDuringFiscalYearMember_019ddb22-5e29-7a15-9a24-d16bf3a8c181" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_FairValueAsOfPriorFiscalYearEndOfOptionAwardsAndStockAwardsGrantedInPriorFiscalYearsThatFailedToMeetApplicableVestingConditionsDuringFiscalYearMember_019ddb22-5e29-75d0-ba40-4cbd26b66957" xlink:href="crto-20260508.xsd#crto_FairValueAsOfPriorFiscalYearEndOfOptionAwardsAndStockAwardsGrantedInPriorFiscalYearsThatFailedToMeetApplicableVestingConditionsDuringFiscalYearMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_crto_FairValueAsOfPriorFiscalYearEndOfOptionAwardsAndStockAwardsGrantedInPriorFiscalYearsThatFailedToMeetApplicableVestingConditionsDuringFiscalYearMember_019ddb22-5e29-75d0-ba40-4cbd26b66957" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_crto_ValueOfDividendsOrOtherEarningsPaidOnStockOrOptionAwardsNotOtherwiseReflectedInFairValueOrTotalCompensationMember_019ddb22-5e29-731a-93e0-5e79c3c93b54" xlink:href="crto-20260508.xsd#crto_ValueOfDividendsOrOtherEarningsPaidOnStockOrOptionAwardsNotOtherwiseReflectedInFairValueOrTotalCompensationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllAdjToCompMember" xlink:to="loc_crto_ValueOfDividendsOrOtherEarningsPaidOnStockOrOptionAwardsNotOtherwiseReflectedInFairValueOrTotalCompensationMember_019ddb22-5e29-731a-93e0-5e79c3c93b54" xlink:type="arc" order="11"/>
  </link:definitionLink>
</link:linkbase>
