Cleon II is a fictional character from Isaac Asimov's Foundation Series. He is the last strong monarch of the Galactic Empire, and reigned during the time when Bel Riose, the last great Imperial general, was engaging in a successful campaign against the early Foundation. Cleon becomes wary of Riose's success, and has him recalled and executed. Following Cleon's death, the Empire falls into a civil war.

As the Galactic Empire is based on the Roman Empire, and Bel Riose is based on Belisarius, Cleon II is clearly based on the Eastern Roman Emperor Justinian I. His name however derives from Cleon, an Athenian politician of the Peloponnesian War