Diodorus the Periegete was a Hellenistic geographer active in the 4th or 3rd century BCE. The epithet "Periegete" identifies him as a writer of descriptive geographical guides. No details of his life or origins survive.

His sole known work is the Periegesis of the Inhabited World, a text now lost and preserved only in fragments cited by later authors. Diodorus is a minor figure whose significance lies in his contribution to the Hellenistic genre of periegesis.

His work served as a source for later geographers like Pomponius Mela and Marcianus of Heraclea, aiding the transmission of geographical knowledge from the Hellenistic period to the Roman world and late antiquity.