The Pineiós (Greek: Πηνειός, Latin: Peneus) is a river in Peloponnese, Greece.

[1] Its source is on the southwestern slope of the mountain Erymanthus, near the village Kryovrysi.

It empties into a bay of the Ionian Sea, southwest of Gastouni.

The river passes through the following villages: In the 1960s, the government began building an earth-shaped dam named the Peneus Dam (Φράγμα Πηνειού Fragma Pineiou) to supply water for the north and much of Elis.

In Greek mythology, the Peneus and Alpheus were two rivers re-routed by Heracles in his fifth labour in order to clean the filth from the Augean Stables in a single day, a task which had been presumed to be impossible.