Gaius Pius Esuvius Tetricus was the emperor of the Gallic Empire from 271 to 274 AD. He was originally the praeses (governor) of Gallia Aquitania and became emperor after the murder of Emperor Victorinus in 271, with the support of Victorinus's mother, Victoria. During his reign, he faced external pressure from Germanic raiders, who pillaged the eastern and northern parts of his empire, and the Roman Empire, from which the Gallic Empire had seceded. He also faced increasing internal pressure, which led him to declare his son, Tetricus II, caesar in 273 and possibly co-emperor in 274, although this is debated. The Roman emperor Aurelian invaded in 273 or 274, leading to the Battle of Châlons, at which Tetricus surrendered. Whether this capitulation was the result of a secret agreement between Tetricus and Aurelian or necessary after his defeat is debated. Aurelian spared Tetricus, and even made him a senator and corrector (governor) of Lucania et Bruttium. Tetricus died of natural causes a few years after 274.

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.