Menestheus was an Athenian king in Greek mythology. He was the son of Peteus, grandson of Orneus and great-grandson of King Erectheus. He was installed as King of Athens by Castor and Pollux while Theseus (Menestheus' third cousin) was in the Underworld. Menestheus led the Athenians during the Trojan War and was succeeded as king by Demophon, son of Theseus.