Erymanthos (, ) is a river in the western part of the Peloponnese in Greece. Its source is on the southern slope of the Mount Erymanthos, near the village Agrampela, Achaea. It flows towards the south through a rocky landscape and receives several small tributaries. The river flows into an area rich in pine trees and passes several small mountain villages including Tripotama. Beyond Tripotama it forms the border between Elis and Arcadia. It flows east of the Foloi oak forest. The river empties into the Alfeios 5 km west of the Ladon (river) confluence, near the village Tripotamia.