The Third Sacred War was fought between the forces of the Delphic Amphictyonic League, principally represented by Thebes, and latterly by Philip II of Macedon, and the Phocians. The war was caused by a large fine imposed in 357 BC on the Phocians by the Amphictyonic League, for the offense of cultivating sacred land; refusing to pay, the Phocians instead seized the Temple of Apollo in Delphi, and used the accumulated treasures to fund large mercenary armies. Thus, although the Phocians suffered several major defeats, they were able to continue the war for many years, until eventually all parties were nearing exhaustion. Philip II used the distraction of the other states to increase his power in northern Greece, in the process becoming ruler of Thessaly. In the end, Philip's growing power, and the exhaustion of the other states, allowed him to impose a peaceful settlement of the war, marking a major step in the rise of Macedon to pre-eminence in Ancient Greece.

Delphi, in legend previously called Pytho (Πυθώ), was an ancient sacred precinct and the seat of Pythia, the major oracle who was consulted about important decisions throughout the ancient classical world. The ancient Greeks considered the centre of the world to be in Delphi, marked by the stone monument known as the Omphalos of Delphi (navel).