Legio I Flavia Pacis: one of the legions of the later Roman empire. Its name means "the Flavian legion of virtue".
This legion belongs to a series that also included I Flavia Pacis and III Flavia Salutis. The three legions were probably formed by the emperor Constantius II (337-361) and fought in the eastern half of the Roman empire.
It is possible that this legion is identical to the Second Flavian Legion that, together with II Armeniaca and II Parthica, defended Bezabde (modern Cizre) on the Tigris, and was unable to prevent its capture by the Persians (360).