Cleisthenes (also Clisthenes or Kleisthenes) is a noble Athenian of the Alcmaeonid family.

He is credited with reforming the constitution of ancient Athens and setting it on a democratic footing in 508/7 BCE.

For these accomplishments, historians refer to him as "the father of Athenian democracy."

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.

Also, he was credited for increasing power of assembly and he also broke up power of nobility for Athens.