ñ-Amyrin synthase (, 2,3-oxidosqualene alpha-amyrin cyclase, mixed amyrin synthase) is an enzyme with systematic name (3S)-2,3-epoxy-2,3-dihydrosqualene mutase (cyclizing, alpha-amyrin-forming). This enzyme catalyses the following chemical reaction
This multifunctional enzyme produces both alpha- and beta-amyrin.