Domitius Modestus (Greek: Δομίτιος Μοδέστος; floruit 358–377) was a politician of the Roman Empire. He held appointments under the emperors Constantius II, Julian, and Valens, and was consul in 372. Previously a pagan, he converted to Arianism under Valens, and was sent by Valens to mediate between the Arian and Nicene factions with Basil of Caesarea.