The Olvios (Greek: Όλβιος) is a river that flows in western Corinthia in the northern Peloponnese in Greece.

The river empties into the Feneos plain, once an area of swamps, now containing farmlands.

The river begins on the Mavro Oros mountain, south of Evrostina.

The river empties into the Feneos Fields northwest of the Oligyrtos mountains.

The Olvios flows along the villages of Karya, Kato Tarsos, Steno, Feneos, Goura and Mesino.