In enzymology, an ent-copalyl diphosphate synthase (EC 5.5.1.13) is an enzyme that catalyzes the chemical reaction: Hence, this enzyme has one substrate, geranylgeranyl pyrophosphate, and one product, . This enzyme participates in gibberellin biosynthesis. This enzyme belongs to the family of isomerases, specifically the class of intramolecular lyases. The systematic name of this enzyme class is ent-copalyl-diphosphate lyase (decyclizing). Other names in common use include ent-kaurene synthase A, and ent-kaurene synthetase A.