Which Spartan king was killed at the Battle of Thermopylae in 480 BCE?

Leonidas I was the Spartan king killed at the Battle of Thermopylae in 480 BCE. He commanded the Greek force that attempted to block the Persian invasion through the narrow pass.

Leonidas belonged to Sparta’s Agiad royal house and became king after the death of his half-brother Cleomenes I. At Thermopylae, his force included 300 Spartan citizens, but the wider Greek defense involved contingents from several other communities. The pass was eventually outflanked, and Leonidas died with the remaining defenders.

The battle did not stop the Persian invasion permanently, but it became a powerful example of resistance and sacrifice. Thermopylae is often simplified as a battle fought only by 300 Spartans; that popular image leaves out the other Greek troops who participated and the additional defenders who remained in the final phase.