The Gallic Empire or the Gallic Roman Empire are names used in modern historiography for a breakaway part of the Roman Empire that functioned de facto as a separate state from 260 to 274. It originated during the Crisis of the Third Century, when a series of Roman military leaders and aristocrats declared themselves emperors and took control of Gaul and adjacent provinces without attempting to conquer Italy or otherwise seize the central Roman administrative apparatus.

The Gallic Empire was established by Postumus in 260 in the wake of barbarian invasions and instability in Rome, and at its height included the territories of Germania, Gaul, Britannia, and (for a time) Hispania. After Postumus' assassination in 269 it lost much of its territory, but continued under a number of emperors and usurpers. It was retaken by Roman emperor Aurelian after the Battle of Châlons in 274.