<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:ns2="http://www.sec.gov/edgar/common">
    <headerData>
        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001991131</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0001835830</issuerCik>
            <issuerName>KLAVIYO INC</issuerName>
            <secFileNumber>001-41806</secFileNumber>
            <issuerAddress>
                <ns2:street1>125 Summer Street, 6th Floor</ns2:street1>
                <ns2:city>Boston</ns2:city>
                <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                <ns2:zipCode>02110</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>6172131788</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>AMANDA WHALEN</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC Executive Financial Services</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>8th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>60000</noOfUnitsSold>
            <aggregateMarketValue>2109600.00</aggregateMarketValue>
            <noOfUnitsOutstanding>78803963</noOfUnitsOutstanding>
            <approxSaleDate>11/18/2024</approxSaleDate>
            <securitiesExchangeName>NYSE</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>08/15/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Restricted Stock Units</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>60000</amountOfSecuritiesAcquired>
            <paymentDate>08/15/2024</paymentDate>
            <natureOfPayment>N/A</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>10b5-1 Sales for AMANDA WHALEN</name>
                <address>
                    <ns2:street1>125 Summer Street, 6th Floor</ns2:street1>
                    <ns2:city>Boston</ns2:city>
                    <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                    <ns2:zipCode>02110</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>10/04/2024</saleDate>
            <amountOfSecuritiesSold>10000</amountOfSecuritiesSold>
            <grossProceeds>353614.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>10b5-1 Sales for AMANDA WHALEN</name>
                <address>
                    <ns2:street1>125 Summer Street, 6th Floor</ns2:street1>
                    <ns2:city>Boston</ns2:city>
                    <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                    <ns2:zipCode>02110</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <saleDate>09/06/2024</saleDate>
            <amountOfSecuritiesSold>10000</amountOfSecuritiesSold>
            <grossProceeds>297221.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <remarks>The securities to be sold were acquired upon the vesting of restricted stock units during the period of 08/15/2024 through 11/15/2024.
</remarks>
        <noticeSignature>
            <noticeDate>11/18/2024</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>08/16/2024</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Amanda Whalen</signature>
        </noticeSignature>
    </formData>
</edgarSubmission>
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144
0001991131
XXXXXXXX
LIVE
0001835830
KLAVIYO INC
001-41806
125 Summer Street, 6th Floor
Boston
MA
02110
6172131788
AMANDA WHALEN
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
60000
2109600.00
78803963
11/18/2024
NYSE
Common
08/15/2024
Restricted Stock Units
Issuer
N
60000
08/15/2024
N/A
N
10b5-1 Sales for AMANDA WHALEN
125 Summer Street, 6th Floor
Boston
MA
02110
Common
10/04/2024
10000
353614.00
10b5-1 Sales for AMANDA WHALEN
125 Summer Street, 6th Floor
Boston
MA
02110
Common
09/06/2024
10000
297221.00
The securities to be sold were acquired upon the vesting of restricted stock units during the period of 08/15/2024 through 11/15/2024.
11/18/2024
08/16/2024
/s/ Amanda Whalen