<SEC-DOCUMENT>0001470831-26-000249.txt : 20260305
<SEC-HEADER>0001470831-26-000249.hdr.sgml : 20260305
<ACCEPTANCE-DATETIME>20260305213432
ACCESSION NUMBER:		0001470831-26-000249
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20260305
FILED AS OF DATE:		20260305
DATE AS OF CHANGE:		20260305

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Edmond Landon
		CENTRAL INDEX KEY:			0001991399
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-41806
		FILM NUMBER:		26728301

	MAIL ADDRESS:	
		STREET 1:		KLAVIYO, INC.
		STREET 2:		125 SUMMER STREET, 6TH FLOOR
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02110

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Klaviyo, Inc.
		CENTRAL INDEX KEY:			0001835830
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PREPACKAGED SOFTWARE [7372]
		ORGANIZATION NAME:           	06 Technology
		EIN:				000000000
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		125 SUMMER STREET, FLOOR 6
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02110
		BUSINESS PHONE:		800-338-1744

	MAIL ADDRESS:	
		STREET 1:		125 SUMMER STREET, FLOOR 6
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02110
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wk-form4_1772764470.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-03-05</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001835830</issuerCik>
        <issuerName>Klaviyo, Inc.</issuerName>
        <issuerTradingSymbol>KVYO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001991399</rptOwnerCik>
            <rptOwnerName>Edmond Landon</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O KLAVIYO, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>125 SUMMER STREET, 6TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02110</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Legal Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>1</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Series A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-03-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>15093</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>20.16</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>326728</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">These transactions were effected by the Reporting Person pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on August 21, 2025.</footnote>
        <footnote id="F2">The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $20.00 to $20.63 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.</footnote>
        <footnote id="F3">Consists of (i) 98,321 shares of the Issuer's Series A Common Stock, par value $0.001 per share (&quot;Series A Common Stock&quot;), and (ii) 228,407 unvested restricted stock units awarded under the Issuer's 2023 Stock Option and Incentive Plan, each representing the contingent right to receive one share of Series A Common Stock upon vesting and settlement.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Landon Edmond</signatureName>
        <signatureDate>2026-03-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
