Polycrates (/pəˈlɪkrəˌtiːz/; Greek: Πολυκράτης), son of Aeaces, was the tyrant of Samos from c. 538 BC to 522 BC. He had a reputation as both a fierce warrior and an enlightened tyrant.
He took power during a festival of Hera with his brothers Pantagnotus and Syloson, but soon had Pantagnotus killed and exiled Syloson to take full control for himself. He then allied with Amasis II, Pharaoh of Egypt, as well as the tyrant of Naxos Lygdamis. With a navy of 100 penteconters and an army of 1,000 archers, he plundered the islands of the Aegean Sea and the cities on the Ionian coast of Asia Minor, defeating and enslaving the navies of Lesbos and Miletus. He also conquered the small island of Rhenea, which he chained to nearby Delos as a dedication to Apollo.
On Samos Polycrates built an aqueduct, a large temple of Hera (the Heraion, to which Amasis dedicated many gifts), and a palace later rebuilt by the Roman emperor Caligula. In 522 BC he celebrated an unusual double festival in honour of the god Apollo of Delos and of Delphi; it has been suggested that the Homeric Hymn to Apollo, sometimes attributed to Cynaethus of Chios, was composed for this occasion. Polycrates was probably a patron of the poets Anacreon, and Ibycus and of the Crotonian doctor Democedes.