11,12-epoxy-3-methylcholanthrene is an organic heterohexacyclic compound that is 3-methylcholanthrene which has undergone epoxidation by the formal 1,2-addition of an oxygen atom to the double bond at the 11-12 position. It has a role as a mutagen. It is an epoxide and an organic heterohexacyclic compound. It is functionally related to a 3-methylcholanthrene.