Magnus Maximus (Latin: Flavius Magnus Maximus Augustus) (ca.

335 – August 28, 388), also known as Maximianus and Macsen Wledig in Welsh, is Western Roman Emperor from 383 to 388.

In 383, as commander of Britain, he usurps the throne against emperor Gratian; and through negotiation with emperor Theodosius I the following year he is made emperor in Britannia and Gaul - while Gratian's brother Valentinian II retains Italy, Pannonia, Hispania, and Africa.

In 387, Maximus' ambitions lead him to invade Italy, resulting in his defeat by Theodosius I at the Battle of the Save in 388.

His death marks the end of real imperial activity in northern Gaul and Britain.

After Maximus, no significant Roman emperor (ignoring shadowy and short-lived usurpers) ever goes north of Lyons again.