In Greek mythology, Epeius (Ancient Greek: Ἐπειός) was an Elean prince, son of King Endymion, who won a footrace at Olympia against his brothers Aetolus and Paeon for their father's kingdom. His subjects were named Epeans for the first time after him. He is distinct from Epeius son of Panopeus, the builder of the Wooden Horse.
Adapted from Wikipedia, "Epeius" · CC BY-SA 4.0
I.Race for the throne
Pausanias gathers the Elean account: all agree that Endymion begat Paeon, Epeius, Aetolus, and a daughter Eurycyda. Endymion set his sons to race at Olympia for the kingdom; Epeius won, obtained the throne, and his subjects were named Epeans for the first time (Description of Greece 5.1.4). Of his brothers, Aetolus remained at home while Paeon, vexed at his defeat, went into distant exile, and the region beyond the Axius was named Paeonia after him.
II.Reign
Epeius married Anaxiroe daughter of Coronus and begat a daughter Hyrmina (Hyrmine) but no male issue. In his reign Oenomaus was lord of Pisa until Pelops, crossing from Asia, overthrew Oenomaus and separated Pisa and Olympia from the Epean kingdom. On Epeius' death Aetolus came to the throne, before himself fleeing the Peloponnese after unintentionally killing Apis at the games of Azan (Pausanias 5.1.6–5.1.8).
III.Homonyms
This atlas entry (epeius-endymion) is the Elean king, son of Endymion. Distinct from Epeius son of Panopeus (epeius), the Phocian boxer and architect who built the Wooden Horse at Troy — Homer's and Apollodorus' craftsman of the horse, with no share in the Elean royal stem.