The Amphictyonic League (Amphictyony) was a form of Greek Hellenic religious organization that was formed to support specific temple or sacred place. Members met at stated times in the same sanctuary to keep religious festivals and conduct other matters as well. The most famous was the Delphic or Great Amphictyonic League that was formed to support greater temples of Apollo and Demeter. League council had religious authority and power to declare punishment against offenders. Punishment could range from fines to expulsion to sacred war.

The Great Amphictyonic League was founded circa 1100 BC for the protection and administration of the temple of Apollo in Delphi and temple of Demeter in Anthela , near Thermopylae. Contemporary legends claimed that it was founded by Amphictyon, brother of Hellen, the common ancestor of all Hellenes. Representatives of twelve members met in Thermopylae at spring and in Delphi at autumn.

Original founders were Aenianes or Oetoeans , Boeotians (of Thebes), Dolopes , Dorians (of Sparta), Ionians (of Athens), Locrians , Magnetians , Malians, Perrhoebians , Phocians, Pythians (of Delphi) and Thessalians. The League doctrine required that no member would be entirely wiped out in war and no water supply of any member would be cut even in wartime. It did not prevent members from fighting about the dominance over the temples.

Originally religious organization became politically important in the 6th century BC when larger city-states begun to use it to apply pressure to the lesser ones. In 356 BC Phocians captured and sacked Delphi and sacred war was declared against them. After a ten-year war Phocians were expelled from the League in 346 BC and their two votes were given to Macedonians who had helped to defeat them. Philip II of Macedonia used its power to further his expansionistic conquests in Greece. 279 BC Phocians were readmitted after they defended Delphi against Gaul attack and Aetolians, who already dominated the Delphi sanctuary, were admitted as new members.

By 191 BC League had 17 members but only the most dominant one had the two votes, when others had only one.

The league continued to exist under Roman Empire but its authority was limited to the care of the Apollo temple. Roman emperor Augustus incorporated the Aenianes, Malians, Magnetians and Pythians with Thessalians. Since Dolopes had vanished, he gave their position to city of Nicopolis.

The Amphictyonic League vanished some time in the AD 2nd century .