In Greek mythology, Demophon (Δημοφόων) referred to three different kings:.
Demophon of Eleusis
Demophon was a son of King Celeus and Queen Metanira. While Demeter was searching for her daughter, having taken the form of an old woman called Doso, she received a hospitable welcome from Celeus, the King of Eleusis in Attica. He asked her to nurse Demophon and Triptolemus, his sons by Metanira. As a gift to Celeus, because of his hospitality, Demeter planned to make Demophon immortal by burning his mortal spirit away in the family hearth every night. She was unable to complete the ritual because Metanira walked in on her one night. Instead, Demeter chose to teach Triptolemus the art of agriculture and, from him, the rest of Greece learned the plant and reap crops. He flew across the land on a winged chariot while Demeter and Persephone cared for him, and helped him complete his mission of educating the whole of Greece on the art of agriculture.
Demophon son of Theseus
Demophon, according to Pindar, son of Theseus and half brother of Acamas, fought in the Trojan War