3rd-century BC confederation of towns of Achaea, an area in the northern Peloponnese of ancient Greece.
Twelve cities had joined together by the 4th century BC to combat piracy, but they disbanded after the death of Alexander the Great . Ten cities renewed the league in 280 BC, later admitting non-Achaean cities to defend themselves against Macedonia, then Sparta, and finally Rome. Rome dissolved the league after defeating it in 146 BC. Later a smaller league was formed that existed into the Roman imperial age.