<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2022-05-03</periodOfReport>

    <issuer>
        <issuerCik>0001790177</issuerCik>
        <issuerName>RiverNorth Flexible Municipal Income Fund, Inc.</issuerName>
        <issuerTradingSymbol>RFM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001769190</rptOwnerCik>
            <rptOwnerName>Lawlor John J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MACKAY SHIELDS LLC</rptOwnerStreet1>
            <rptOwnerStreet2>1345 AVENUE OF THE AMERICAS, 42ND FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10105</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOther>true</isOther>
            <otherText>Portfolio Manager</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-05-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>17.169</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The shares were sold in separate transactions. The range of prices for the transactions reported on May 3, 2022 was $17.16 to $17.20. The Reporting Person undertakes to provide upon request by the Commission staff, the issuer, or a security holder of the issuer, full information regarding the number of shares purchased at each separate price.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ John Lawlor by his Attorney-In-Fact - Chris Fitzgerald, Managing Director, CCO</signatureName>
        <signatureDate>2022-05-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
