Thermopylae a pass between the mountains and the sea in Greece, about 200 km (120 miles) north-west of Athens, originally narrow but now much widened by the recession of the sea. In 480 bc it was the scene of the defence against the Persian army of Xerxes I by 6,000 Greeks; among them were 300 Spartans, all of whom, including their king Leonidas, were killed.

The pass was the traditional invasion route from northern Greece and was subsequently used by the Gauls in 279 bc and by Cato the Elder in 191 bc.

Thermopylae Strategic mountain pass in e central Greece, site of several battles in ancient times. The most famous was the defence of the pass by Leonidas of Sparta against the Persian invasion of Xerxes I in 480 bc.