In Greek mythology, Perseus (; ), the legendary founder of Mycenae and of the Perseid dynasty of Danaans, was, alongside Cadmus and Bellerophon, the greatest Greek hero and slayer of monsters before the days of Heracles. Perseus beheaded the Gorgon Medusa and saved Andromeda from the sea monster Cetus. Perseus was the son of the mortal Danaë and the god Zeus. He was also the great grandfather of Heracles, also a son of Zeus.