Barbatio (died AD 359) was a Roman general of the infantry under the command of Constantius II. Previously he was a commander of the household troops under Gallus Caesar, but he arrested Gallus under the instruction of Constantius, thereby ensuring his promotion on the death of Claudius Silvanus. In 359, both he and his wife Assyria were arrested and beheaded for treason against Constantius, possibly as part of a plot by Arbitio, a senior cavalry commander, and another exponent of the forms of scheming and political intrigue that became such a part of the later Roman Empire.
Barbatio, a soldier of unknown origin, began his rise when he was appointed to command the household troops of Caesar Gallus, a cousin of the Emperor Constantius II. Constantius was a man of uncertain temperament, highly suspicious of possible rivals, who had been responsible for the execution of many members of his own family after the death of his father Constantine I in 337. Barbatio betrayed his position of trust, beginning a whispering campaign against Gallus, which led to his downfall in 354. According to the account of the historian Ammianus Marcellinus, "Barbatio, after surrounding with armed men all that part of the palace which lay outside of the walls, entered as night was falling, stripped the Caesar of his royal apparel, and dressed him in the tunic and cloak of a common soldier, assuring him, however, with repeated oaths that he had the emperor's authority to tell him that he would suffer nothing further.". Contrary to these assurances, Gallus was taken to Pola, where he was beheaded, and his face mutilated after execution. For his part in the affair, Barbatio was awarded by Constantius with a series of promotions, making him commander of the infantry in Gaul after the death of Claudius Silvanus in 355. According to Ammianus, Barbatio was a man of "rough manners and vaulting ambition, who incurred general hatred by his treacherous betrayal of Caesar Gallus". Having betrayed one Caesar, he soon found himself in a position to attempt to betray another.