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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2019-04-01</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000351834</issuerCik>
        <issuerName>SunOpta Inc.</issuerName>
        <issuerTradingSymbol>STKL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001772678</rptOwnerCik>
            <rptOwnerName>Ennen Joseph</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>7301 OHMS LANE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 600</rptOwnerStreet2>
            <rptOwnerCity>EDINA</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>55439</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Performance Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>892857</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Performance Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>892857</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F7"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F6"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>297619</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.36</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2022-04-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2032-04-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>960061</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The reporting person was granted 892,857 performance stock units (the &quot;Special Performance Units&quot;) as of April 1, 2019. The vesting of the Special Performance Units is subject to (i) the reporting person's continued employment with the Company through December 31, 2022 (the &quot;Performance Period&quot;); and (ii) the satisfaction of certain fiscal year EBITDA performance conditions during the Performance Period. For the EBITDA performance conditions, 297,619 of the Special Performance Units will vest upon the Company achieving annual adjusted EBITDA of $80,000,000, another 297,619 will vest upon the Company achieving annual adjusted EBITDA of $110,000,000, and the final 297,619 will vest upon the Company achieving annual adjusted EBITDA of $140,000,000, and subject to continued employment through the end of the fiscal year the EBITDA performance condition is achieved.</footnote>
        <footnote id="F2">The Performance Stock Units do not have an expiration date.</footnote>
        <footnote id="F3">Performance Stock Units convert into common shares on a one-for-one basis.</footnote>
        <footnote id="F4">The reporting person was granted 892,857 performance stock units (the &quot;Special Performance Units&quot;) as of April 1, 2019. The vesting of the Special Performance Units is subject to (i) the reporting person's continued employment with the Company through December 31, 2022 (the &quot;Performance Period&quot;); and (ii) the satisfaction of certain stock price performance conditions during the Performance Period.  For the stock price performance conditions, 297,619 of the Special Performance Units will vest upon achieving a volume weighted average trading stock price of $5.00 per share, another 297,619 will vest upon achieving a stock price of $9.00 per share, and the final 297,619 will vest upon achieving a stock price of $14.00 per share, in each case for 20 consecutive trading days and subject to continued employment through the date the stock price performance condition is achieved.</footnote>
        <footnote id="F5">The Restricted Stock Units vest in three equal annual installments beginning on April 1, 2020.</footnote>
        <footnote id="F6">The Restricted Stock Units do not have an expiration date.</footnote>
        <footnote id="F7">Restricted Stock Units convert into common shares on a one-for-one basis.</footnote>
    </footnotes>

    <remarks>Exhibit List
     Exhibit 24: Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>/s/ Jill Barnett, attorney-in-fact</signatureName>
        <signatureDate>2019-04-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
