 Ephialtes of Trachis

Ephialtes (; , "Ephialtēs"; although Herodotus spelled it as , "Epialtes") was the son of Eurydemus () of Malis.He betrayed his homeland, in hope of receiving some kind of reward from the Persians, by showing the Persian forces a path around the allied Greek position at the pass of Thermopylae, which helped them win the Battle of Thermopylae in 480 BCE.