Aretades of Cnidus was a historian from the city of Cnidus in Caria. He is believed to have been active sometime between the 4th and 2nd centuries BCE, though his precise dates are unknown. No further biographical details survive.

His sole attested work is On the Tyrants in Sicily, which is now lost. It survives only through fragments and later testimony. According to the Byzantine patriarch Photius, it was a concise, single-volume history covering Sicilian tyrants from Phalaris of Acragas to Dionysius II of Syracuse.

Aretades is a minor historian whose significance rests entirely on this fragmentary work. It served as a source for later compilers like Photius and the Suda, and is occasionally referenced in modern scholarship on the historiography of Sicilian tyranny. The work's extremely fragmentary state limits its independent value.