Epopeus (Ἐπωπεύς) was a mythical Greek king of Sicyon, with an archaic bird-name that linked him to epops (ἔποψ), the hoopoe, the "watcher". A fragment of Callimachus' Aitia ("Origins") appears to ask, "Why, at Sicyon, is it the hoopoe, and not the usual "splendid ravens", that is the bird of good omen?"

Epopeus was in fact the most memorable king at Sicyon and features in Euripides' Antiope. He founded a sanctuary of Athena on the Sicyonian acropolis where he performed victory rites, celebrating his victory over Theban intruders. Athena caused olive oil to flow before the shrine.

At Titane in Sicyonia, Pausanias saw an altar, in front of it a tumulus raised to the hero Epopeus, and, near to the barrow-tomb, the "Gods of Aversion"—the apotropai—"before whom are performed the ceremonies which the Hellenes observe for the averting of evils". In the etiological myth that accounted for the origin of rituals propitiating the daimon of Epopeus, it was told that Zeus impregnated Antiope, who, being the wife of Nycteus, fled in shame to Epopeus, king of Sicyon, abandoning her children, Amphion and Zethus. They were exposed on Mount Cithaeron, but, in a familiar mytheme, were found and brought up by a shepherd. Nycteus, unable to retrieve his wife, sent his brother Lycus to take her. He did so and gave her as a slave to his own wife, Dirce.