Cleisthenes (Greek: Κλεισθένης, also Clisthenes or Kleisthenes) was a noble Athenian of the Alcmaeoni family. He is credited with reforming the constitution of ancient Athens and setting it on a democratic footing in 508 BC or 507 BC. He was the maternal grandson of the tyrant Cleisthenes of Sicyon, as the younger son of the latter's daughter Agariste and her husband Megacles.