Demophanes (died 428 BC) was a 5th-century BC Elean Greek man who served as a judge of the Olympic Games. Demophanes was a friend of Alcibiades and the former Olympic champion Kallias, and, during the Olympic Games of 428 BC, he drank with Alcibiades and Kallias at the Leonidaion. However, he died by poisoning committed by Kallias as part of a scheme by the Cult of Kosmos to reassert its power; Alcibiades, conversely, survived with the help of an antidote retrieved by the mercenary Kassandra.