The Battle of Prousidon was a battle of the Peloponnesian War which was fought in Elis in 422 BC.
Following the Battle of Amphipolis, during which both the Spartan general Brasidas and the Athenian leader Cleon were killed, both Athens and Sparta's desire for continued war began to decline. However, the animosity between the two poleis was too great to overcome, and Sparta attempted to press its advantage by invading Athenian-held Elis in the western Peloponnese. The two armies met in battle at Prousidon, with the Spartans hiring the mercenary Kassandra the Eagle Bearer as their champion, and the Athenians turning to Proteos the Wing-Footed. In the ensuing battle, Kassandra slew Proteos, 5 Athenian captains, and 22 soldiers, turning the tide of battle in Sparta's favor. The Spartans destroyed the Athenian garrison army and reclaimed Elis, leading to Athens retaliating with an invasion of Arcadia.