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    <submissionType>144</submissionType>
    <filerInfo>
      <filer>
        <filerCredentials>
          <cik>0001861730</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
      </filer>
      <liveTestFlag>LIVE</liveTestFlag>



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    <issuerInfo>
      <issuerCik>0001842718</issuerCik>
      <issuerName>INTEGRAL AD SCIENCE HOLDING CORP.</issuerName>
      <secFileNumber>001-40557</secFileNumber>
      <issuerAddress>
        <com:street1>99 WALL STREET</com:street1>
        <com:street2>#1950</com:street2>
        <com:city>NEW YORK</com:city>
        <com:stateOrCountry>NY</com:stateOrCountry>
        <com:zipCode>10005</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>(646) 278-4871</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>SHARMA TOM</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <relationshipToIssuer>Officer</relationshipToIssuer>
      </relationshipsToIssuer>
    </issuerInfo>
    <securitiesInformation>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <brokerOrMarketmakerDetails>
        <name>Fidelity Brokerage Services LLC</name>
        <address>
          <com:street1>900 Salem Street</com:street1>
          <com:city>Smithfield</com:city>
          <com:stateOrCountry>RI</com:stateOrCountry>
          <com:zipCode>02917</com:zipCode>
        </address>
      </brokerOrMarketmakerDetails>
      <noOfUnitsSold>8269</noOfUnitsSold>
      <aggregateMarketValue>121307.06</aggregateMarketValue>
      <noOfUnitsOutstanding>156650162</noOfUnitsOutstanding>
      <approxSaleDate>08/07/2023</approxSaleDate>
      <securitiesExchangeName>NASDAQ</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>08/02/2023</acquiredDate>
      <natureOfAcquisitionTransaction>Restricted Stock Vesting</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>8269</amountOfSecuritiesAcquired>
      <paymentDate>08/02/2023</paymentDate>
      <natureOfPayment>Compensation</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Kshitij Sharma</name>
        <address>
          <com:street1>12 E 49th Street</com:street1>
          <com:street2>20th Floor</com:street2>
          <com:city>New York</com:city>
          <com:stateOrCountry>NY</com:stateOrCountry>
          <com:zipCode>10017</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>05/22/2023</saleDate>
      <amountOfSecuritiesSold>9646</amountOfSecuritiesSold>
      <grossProceeds>167887.67</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Kshitij Sharma</name>
        <address>
          <com:street1>12 E 49th Street</com:street1>
          <com:street2>20th Floor</com:street2>
          <com:city>New York</com:city>
          <com:stateOrCountry>NY</com:stateOrCountry>
          <com:zipCode>10017</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>05/23/2023</saleDate>
      <amountOfSecuritiesSold>13452</amountOfSecuritiesSold>
      <grossProceeds>237718.36</grossProceeds>
    </securitiesSoldInPast3Months>
    <remarks>Tom Sharma and Kshitij Sharma are one and the same person</remarks>
    <noticeSignature>
      <noticeDate>08/07/2023</noticeDate>
      <signature>/S/ Adam Gehring, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Kshitij Sharma</signature>
    </noticeSignature>
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144
0001861730
XXXXXXXX
LIVE
0001842718
INTEGRAL AD SCIENCE HOLDING CORP.
001-40557
99 WALL STREET
#1950
NEW YORK
NY
10005
(646) 278-4871
SHARMA TOM
Officer
Common
Fidelity Brokerage Services LLC
900 Salem Street
Smithfield
RI
02917
8269
121307.06
156650162
08/07/2023
NASDAQ
Common
08/02/2023
Restricted Stock Vesting
Issuer
N
8269
08/02/2023
Compensation
N
Kshitij Sharma
12 E 49th Street
20th Floor
New York
NY
10017
Common
05/22/2023
9646
167887.67
Kshitij Sharma
12 E 49th Street
20th Floor
New York
NY
10017
Common
05/23/2023
13452
237718.36
Tom Sharma and Kshitij Sharma are one and the same person
08/07/2023
/S/ Adam Gehring, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Kshitij Sharma