Flavius Valerius Severus (died September 307), also called Severus II, was a Roman emperor from 306 to 307, and a member of the Tetrarchy. He shared control of the western half of the empire with Constantine I, but spent most of his short reign in a civil war against the usurper Maxentius, who later killed him and took over Italy.
Background and early career
Severus was of humble birth, born in Northern Illyria around the middle of the third century. A friend of emperor Galerius, he rose to become a senior officer in the Roman army, Diocletian acquiesced and Severus succeeded to the post of caesar on 1 May 305, thus becoming the junior colleague of Constantius I, augustus of the western half of empire.
When Maxentius, the son of the retired emperor Maximian, revolted at Rome in October, Galerius sent Severus to suppress the rebellion. Severus moved towards Rome from his capital, Mediolanum, at the head of an army previously commanded by Maximian. Despite Maximian's assurance, Severus was nonetheless displayed as a captive and later imprisoned at Tres Tabernae, near the current Cisterna di Latina. One belief is that when Galerius himself invaded Italy to suppress Maxentius and Maximian, the former ordered Severus's death.
The position of Western augustus remained officially vacant until the Conference of Carnuntum of November 308, in which Licinius was appointed as new emperor (although his western domains only consisted of the Balkan Peninsula). Severus was survived by his son Flavius Severianus, but he was later executed by Licinius for treason.