A mythological Greek hero, son of Aeson, king of Iolcos; brought up by the centaur Chiron, was supplanted on the throne by his half-brother Pelias; undertook the leadership of the Argonautic expedition, assisted by Medea in this enterprise; he took her to wife, but cast her off for Creusa, whom Medea to avenge herself killed, with her father and her two sons by Jason, she herself escaping to Athens in a chariot drawn by winged dragons; Jason took refuge from her fury in the sanctuary of Poseidon near Corinth, where the timber of the ship Argo deposited there breaking up fell upon him and crushed him to death.