Boeotian League, league that first developed as an alliance of sovereign states in Boeotia, a district in east-central Greece, about 550 bc, under the leadership of Thebes. After the defeat of the Greeks at Thermopylae, Thebes and most of Boeotia sided with the Persians during the Persian invasions of 480 and 479. Subsequently, the victorious Greeks dissolved the Boeotian League as punishment. The Boeotians remained weak until 446, when they revolted against Athenian domination and reconstituted the league in alliance with Sparta. The league later opposed Sparta in the Corinthian War (395–387) and was defeated and again dissolved, Sparta having had Persian help.
Before the Corinthian War the league had grown into a close-knit confederacy, organized in 11 districts by 431. Each district, comprising one or more cities, sent a general (boeotarch), several judges, and 60 counselors to a federal government; the federal council of 660 was probably divided into four panels, each in turn convening for one year. The vote was given only to the propertied classes. Thebes, where the council met, dominated the league since it controlled four districts and supplied the best contingent to the federal army.
In 379 Thebes joined Athens in a successful effort to overturn Spartan supremacy in Greece. The league was then reconstituted on an initially successful democratic basis: all Boeotians, whatever their property, were members of an assembly convened at Thebes; their vote decided all matters of policy. The seven-man executive (one from each of the then seven districts, of which Thebes controlled three) was directly responsible to the Assembly. Other districts under federal systems joined Boeotia: Euboea, Acarnania, Phocis, Thessaly, Arcadia, and Achaea. But this great block of military power was soon split by imperialist ambitions, and the Boeotian League itself destroyed Orchomenus (364) and intervened in the Achaean League (366) and Arcadian League (362).
Decline set in rapidly when Phocis hired mercenaries and ravaged Boeotia in the Sacred War (355–346), which Philip II of Macedon ended as an ally of Thebes. Thebes suffered defeat, however, along with Athens, when Philip quelled their efforts to maintain Greek independence in 338 at the Battle of Chaeronea. The Boeotian League was again dissolved, and after an abortive revolt (335) against Alexander the Great of Macedon, Thebes and the rest of Boeotia fell permanently under external domination.