To Justin (Marcus Junian(i)us Justinus), otherwise unknown, is attributed our abbreviated version of the lost Philippic History by (Gnaeus?) Pompeius Trogus, a massive account, in forty-four books, of the non-Roman world and its civilizations, from mythic beginnings through Alexander the Great, the Hellenistic kingdoms, and Parthia. Trogus' work thus complemented the monumental history of Rome by his Augustan contemporary, Livy, and in high style traced similar moral themes: rulers and states that lack such virtues as moderation, justice, and piety bring harm or ruin on themselves, and often on their realms as well.

Justin, working at some time in the late second to the late fourth century AD, did not produce a strict epitome or summary but what he calls "a brief anthology" not unlike Florus (LCL 231), who used Livy's history as the primary source for a brief but original military history of Rome, Justin freely selected what suited his own purposes, favoring "what makes pleasurable reading or serves to provide a moral," with an eye to the kind of emotive anecdotes that might be useful to orators. He also blends Trogus' language with borrowings from literature of subsequent generations. Justin's anthology became one of the most widely read and influential books in the Middle Ages and Renaissance, indeed the main authority on world history other than Roman, surviving in more than 200 manuscripts.

Also included in this edition are the "Prologues," summaries of Trogus by some other compiler, which preserve many details that Justin omits or reports differently.