Yes. Although it’s prudent to have a marriage agreement (also known as a marriage contract) before you get married, it’s not essential. You can get married without one. This means you can also get divorced without one.
But if you are actually referring to a marriage certificate – meaning one of the documents that you needed in order to get legally married in Ontario – then, yes: You do need to provide a copy of your original marriage certificate with your Divorce Application, or in rare circumstances you may be able to provide a sworn affidavit as to why you cannot provide a copy.