Cleon (; Greek: Κλέων Kleon, Ancient Greek: [kléɔːn]) was a tyrant of the ancient Greek city-state of Sicyon in the 3rd century BC. He came to power as commander of the Macedonian garrison after the conquest of the city by Demetrius Poliorcetes in 303/302 BC. Cleon governed Sicyon for some twenty years until he was assassinated. On his death he was followed by two more tyrants, Euthydemus and Timocleidas, who ruled jointly until they were expelled by a democratic revolt.