The Thessalian League was an ancient Greek confederation formed by the city-states of Thessaly, a region in central Greece. Established in the 5th century BCE, it aimed to unify the Thessalian cities for mutual defense and political cooperation. The League was notable for its military strength, particularly its cavalry, which played a significant role in various battles during the classical period. The League was governed by a council and had a central assembly where representatives from member cities convened. It was influential in the broader context of Greek politics, especially during conflicts like the Peloponnesian War. The League's prominence declined after the rise of Macedonia under Philip II.