Melanthius the Historian was a 4th-century BCE Greek historian. His existence is attested solely by a single citation in Athenaeus of Naucratis's Deipnosophistae, which provides no details on his birthplace or life.

His only known work, now lost, was a history or a treatise concerning Dionysius I, tyrant of Syracuse. Athenaeus cites it for information on the luxurious dining practices of the Syracusan court.

Melanthius's significance lies entirely in his status as a lost source, representative of many minor, specialized historians whose works survive only in fragments. His citation provides a minor datum for historiographical interest in Sicilian tyrants.