<SEC-DOCUMENT>0001288847-17-000060.txt : 20170316
<SEC-HEADER>0001288847-17-000060.hdr.sgml : 20170316
<ACCEPTANCE-DATETIME>20170316183638
ACCESSION NUMBER:		0001288847-17-000060
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170315
FILED AS OF DATE:		20170316
DATE AS OF CHANGE:		20170316

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Five9, Inc.
		CENTRAL INDEX KEY:			0001288847
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER PROCESSING & DATA PREPARATION [7374]
		IRS NUMBER:				943394123
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		4000 EXECUTIVE PKWY.
		STREET 2:		SUITE 400
		CITY:			SAN RAMON
		STATE:			CA
		ZIP:			94583
		BUSINESS PHONE:		9252012000

	MAIL ADDRESS:	
		STREET 1:		4000 EXECUTIVE PKWY.
		STREET 2:		SUITE 400
		CITY:			SAN RAMON
		STATE:			CA
		ZIP:			94583

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	Five 9 Inc
		DATE OF NAME CHANGE:	20040428

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Burkland Michael
		CENTRAL INDEX KEY:			0001604097

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-36383
		FILM NUMBER:		17695956

	MAIL ADDRESS:	
		STREET 1:		C/O FIVE9, INC.
		STREET 2:		4000 EXECUTIVE PARKWAY, SUITE 400
		CITY:			SAN RAMON
		STATE:			CA
		ZIP:			94583
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_148970378443228.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-03-15</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001288847</issuerCik>
        <issuerName>Five9, Inc.</issuerName>
        <issuerTradingSymbol>FIVN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001604097</rptOwnerCik>
            <rptOwnerName>Burkland Michael</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FIVE9, INC. BISHOP RANCH 8, 4000</rptOwnerStreet1>
            <rptOwnerStreet2>EXECUTIVE PARKWAY, SUITE 400</rptOwnerStreet2>
            <rptOwnerCity>SAN RAMON</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94583</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO, President and Chairman</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>24000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>16.39</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>48000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>The Burkland Family Revocable Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>988575</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 14, 2016.</footnote>
        <footnote id="F2">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $16.28 to $16.64, inclusive. The reporting person undertakes to provide Five9, Inc., any security holder of Five9, Inc., 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 ranges set forth in this footnote.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ David Hill, attorney-in-fact</signatureName>
        <signatureDate>2017-03-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
