Heracle's stepfather and prince of Tiryns, son of Alcaios.
Amphitryon killed king Electryon of Mycenae by accident at the war against the Taphiae (or Teleboans), and his uncle Sthenelos used this as an excuse to chase him away. He fled to Thebes together with Electryons daughter Alcmene, who promised to marry whoever revenged her brothers who had been killed in the same war their father had been killed in.Amphitryon went after the Taphian king Pterelaos, son of Poseidon, but found that the god had made his son immortal. Poseidon had given Pterelaos a golden hair, that made him immortal as long as it grew on his head. Pterelaos daughter Comaiho fell in love with Amphitryon, and pulled out the golden hair of her fathers head, killing him, but also herself.
On his return to Thebes, he found that Alcmene was not surprised to see him. When he asked why she said he had already visited her the night before and that he had told her of his adventures already. It turned out that Zeus had taken Amphitryons shape, and visited Alcmene. As a result of this, Alcmene gave birth to two sons: Heracles by Zeus and Iphicles by Amphitryon.