Roman historian who was the author of Epitome, an abridgment of the Historiae Philippicae et totius mundi origines et terrae situs (Philippic Histories) by Pompeius Trogus (Trogus, Pompeius), whose work is lost. Most of the abridgement is not so much a summary as passages quoted from Trogus, connected by colourless moralizing by Justin. Nothing is known of Justin's personal history other than his work on Trogus's book (chiefly a history of Macedonia and the Hellenistic monarchies, with Parthia), which preserves material that has proved valuable to students of the Hellenistic world. The book was much used in the Middle Ages and survives in more than 200 manuscripts from that period.