Magnus Maximus (335-388) was born in Gallaecia, and would later become a distinguished general serving under Count Theodosius, father of Emperor Theodosius I, fighting in Africa and on the Danube, as well as during the Great Conspiracy in Britain, where he would later be permanently assigned in 380.

When the people became displeased with the western emperor Gratian, his troops proclaimed Maximus emperor, and aided him in his imperial ambitions. Gratian was slain in Lyon, and Maximus later marched into Italy to overthrow Valentinian II. He was only stopped by the intervention of the Eastern Roman Emperor, Theodosius I, who negotiated with him and saw Maximus recognised as co-emperor in the west.

Maximus' ambitions could not be quelled however, and he invaded Italy once more in 387, only to be finally defeated and killed by Theodosius I at the Battle of the Save in 388. To some historians, Maximus' death marked the end of direct imperial presence in Northern Gaul and Britain.