Aetolian League and Achaean League, two rival federations of cities in ancient Greece. The Aetolian League began at the end of the fourth century B.C., when Greece was part of the kingdom of Macedonia. By 250 B.C., most of the Greek towns and villages in north central Greece had become independent and had joined the league. The Achaean League began immediately after the Celtic invasion of 279 B.C. as a confederation of towns on the south shore of the Gulf of Corinth. It grew to encompass all of the Peloponnesus except Sparta, which was independent, and Elis, which belonged to the Aetolian League.

The Aetolian League, fearing Achaean dominance, formed an alliance with Sparta and started a civil war that lasted until 217 B.C. In 195 B.C., the Achaean League incited the Romans to go to war against Sparta. The Aetolian League then turned against Rome and requested aid from the Seleucid kingdom of Syria. In 191 B.C., Seleucid forces marched into Greece, where they were defeated by the Romans. The Aetolian League was dissolved by Rome in 167 B.C.

When a dispute with Sparta developed in 147 B.C., the Achaean League refused to accept Rome's settlement. The next spring the Roman army attacked the league and soundly defeated it. The league was then abolished.