The Battle of the Eurymedon was a double battle, taking place both on water and land, between the Delian League of Athens and her Allies, and the Persian Empire of Xerxes I. It took place in either 469 or 466 BCE, in the vicinity of the mouth of the Eurymedon River (now the Köprüçay) in Pamphylia, Asia Minor. It forms part of the Wars of the Delian League, itself part of the larger Greco-Persian Wars.

In either 469 or 466 BCE, the Persians began assembling a large army and navy for a major offensive against the Greeks. Gathering near the Eurymedon, it is possible that the expedition aimed to move up the coast of Asia Minor, capturing each city in turn. This would bring the Asiatic Greek regions back under Persian control, and give the Persians naval bases from which to launch further expeditions into the Aegean. Hearing of the Persian preparations, the Athenian general Cimon took 200 triremes and sailed to Phaselis in Pamphylia, which eventually agreed to join the Delian League. This effectively blocked the Persian strategy at its first objective.

Cimon then moved to pre-emptively attack the Persian forces near the Eurymedon. Sailing into the mouth of the river, Cimon quickly routed the Persian fleet gathered there. Most of the Persian fleet made landfall, and the sailors fled to the shelter of the Persian army. Cimon then landed the Greek marines and proceeded to attack the Persian army, which was also routed. The Greeks captured the Persian camp, taking many prisoners, and were able to destroy 200 beached Persian triremes. This stunning double victory seems to have greatly demoralised the Persians, and prevented any further Persian campaigning in the Aegean until at least 451 BCE. However, the Delian League do not appear to have pressed home their advantage, probably because of other events in the Greek world that required their attention.