Cambyses I (flourished 6th century BC), Persian king of the Achaemenid dynasty who ruled (circa 600-559 BC) over Anshan (now Baghdad Province, Iraq) as a vassal of the Medes, then preeminent in Persia. Cambyses I was the son of Cyrus I (flourished 7th century BC), whom he succeeded, and the father of Cyrus the Great, who founded the Persian Empire. According to the Greek historian Herodotus, Cambyses I married the daughter of Astyages, king of the Medes (reigned about 584-550 BC).