Theophilus the Historian was a 4th-century BCE author known solely for a single historical work. No biographical details survive beyond this attribution. His only known work is On Sicily, a lost history focusing on Sicilian affairs. It survives only in fragments and testimonia, referenced in the Suda lexicon and by later authors like Athenaeus.

Theophilus is a minor fragmentary historian. His significance lies in his role as a source for regional history; later authors cite On Sicily for details on Sicilian geography, customs, and figures, such as the luxurious habits of the Sybarites. He is often grouped with other local historians of Sicily like Antiochus of Syracuse.