Thermopylae, an ancient pass on the east coast of Greece, famous for the battle that took place there in 480 B.C., during the Persian Wars. Lying about 90 miles (145 km) northwest of Athens, at the head of the Gulf of Lamia, or Malian Gulf, Thermopylae was the major pass between Thessaly and southern Greece. In ancient times the pass was one mile (1.6 km) long and only about 50 feet (15 m) wide; silt deposits have since widened it.

In 480 B.C. the Persians, led by Xerxes, were sweeping southward into Greece. The Spartan king Leonidas mustered the vastly outnumbered Greek forces at Thermopylae, where they held the pass against the Persian attack for three days. Then a Greek traitor led the enemy over the mountains by a little-known path. While the main body of Greeks withdrew to escape the Persian envelopment, Leonidas and his 300 Spartans, supported by 700 Thespians and 400 Thebans, held the Persians at bay but were finally overpowered. Some of the Thebans surrendered; the rest of the Greek warriors fought to the death.

Two other battles were fought here. In 279 B.C. the Greeks held the pass against invading Celts for several months before being defeated. In 191 B.C. the Romans forced the pass against the soldiers of the Seleucid king Antiochus III, an ally of the Aetolian League.