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

    <schemaVersion>X0607</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2026-03-18-05:00</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001780785</issuerCik>
        <issuerName>CN ENERGY GROUP. INC.</issuerName>
        <issuerTradingSymbol>CNEY</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002125418</rptOwnerCik>
            <rptOwnerName>Liu Wenhua</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>true</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>BUILDING 1-B, ROOM 303</rptOwnerStreet1>
            <rptOwnerStreet2>NO. 268 SHINIU  ROAD, LIANDU DISTRICT</rptOwnerStreet2>
            <rptOwnerCity>LISHUI</rptOwnerCity>
            <rptOwnerNonUSStateTerritory></rptOwnerNonUSStateTerritory>
            <rptOwnerCountry>F4</rptOwnerCountry>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription>CHINA</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>Interim CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <ownerSignature>
        <signatureName>/s/ Wenhua Liu</signatureName>
        <signatureDate>2026-05-20</signatureDate>
    </ownerSignature>
</ownershipDocument>
