Cleisthenes (also Clisthenes or Kleisthenes) was the tyrant of Sicyon, who aided in the war against Cirra that destroyed that city in 595 BC. He organized a competition with his daughter Agarista as a prize; the two main competitors for her were the Alcmaeonid Megacles, and Hippocleides. Because Hippocleides made a fool of himself in front of Cleisthenes, Megacles was chosen to marry Agarista.

A relative of Cleisthenes was the later Cleisthenes of Athens.