Zeuxidia amethystus, the commmon saturn, is a species of butterfly in the family Nymphalidae. This butterfly is relatively large and striking. It displays its forewings that have a broad iridescent blue band with a similarl blue patch on the hindwing. It is not abundant in Thailand, Malaysia, Sumatra and Borneo. It has only be observed in dense forests. It can be approached while feeding on fermenting fallen fruits. Its flight period extends from May to September.