See also: Éphialtès

Éphialtès or Éphialte (in Greek old Ἐφιάλτης / Ephiáltês , “nightmare”) was an Athenian statesman which became the chief of the democratic party starting from 465 front J. - C. and which was opposed to the aristocrat Cimon. It should not be confused with the character who betrays Léonidas with the Thermopyles.

Supporting that Sparte was the rival of Athens for hegemony, he fought in vain against the sending of reinforcements to the Spartiates at the time of the revolt of the Hilotes (462).

He benefitted from the absence of Cimon, left for Sparte with four thousand Hoplites of which number of its partisans, or the fall of popularity of this last at the time of its ashamed return, to apply a certain number of radical reforms necessary to the institution of the democracy. He was supported by the young person Périclès.

He persuaded the Parliament to vote laws which withdrew any capacity with the Aréopage and left him simply the jurisdiction in the cases of homicide as well as the administration of the crowned properties. The Aréopage had badly defined attributions and its patriotism at the time of the medic Guerres had been worth a considerable prestige and an influential political role to him though occult. It was the principal support of Cimon and the aristocratic party. Éphialtès made condemn some of its members who were not irreproachable and discredited sufficiently the Aréopage so that him only his legal functions were left. The capacity was allocated thus to the Boulè, the Ekklêsia and the popular courts of justice.

Euménides of Eschyle testify to a certain extent thoughts and feelings waked up by these new measurements.

Éphialtès was assassinated in 461.