Clodius Albinus in the context of "Britannia Inferior"

Lucius Septimius Severus (/səˈvɪərəs/; Latin: [ˈɫuːkiʊs sɛpˈtɪmiʊs sɛˈweːrʊs]; 11 April 145 – 4 February 211) was Roman emperor from 193 to 211. He was born in Leptis Magna, Libya in the Roman province of Africa. As a young man he advanced through the customary succession of offices under the reigns of Marcus Aurelius and Commodus. Severus was the final contender to seize power after the death of the emperor Pertinax in 193 during the Year of the Five Emperors.

After deposing and killing the incumbent emperor Didius Julianus, Severus fought his rival claimants, the Roman generals Pescennius Niger and Clodius Albinus. Niger was defeated in 194 at the Battle of Issus in Cilicia. Later that year Severus waged a short punitive campaign beyond the eastern frontier, annexing the Kingdom of Osroene as a new province. Severus defeated Albinus three years later at the Battle of Lugdunum in Gaul. Following the consolidation of his rule over the western provinces, Severus waged another brief, more successful war in the east against the Parthian Empire, sacking their capital Ctesiphon in 197 and expanding the eastern frontier to the Tigris. He then enlarged and fortified the Limes Arabicus in Arabia Petraea. In 202, he campaigned in Africa and Mauretania against the Garamantes, capturing their capital Garama, and expanding the Limes Tripolitanus along the southern desert frontier of the empire.

The Year of the Five Emperors was AD 193, in which five men claimed the title of Roman emperor: Pertinax, Didius Julianus, Pescennius Niger, Clodius Albinus, and Septimius Severus. This year started a period of civil war when multiple rulers vied for the chance to become emperor.

The political unrest began with the murder of Emperor Commodus on New Year's Eve 192. Once Commodus was assassinated, Pertinax was named emperor, but immediately aroused opposition in the Praetorian Guard when he attempted to initiate reforms. They then plotted his assassination, and Pertinax was killed while trying to reason with the mutineers. He had only been emperor for three months. Didius Julianus, who purchased the title from the Praetorian Guard, succeeded Pertinax, but was ousted by Septimius Severus and executed on 1 June. Severus was declared Caesar by the Senate, but Pescennius Niger was hostile so he declared himself emperor.

The Battle of Lugdunum, also called the Battle of Lyon, was fought on 19 February 197 at Lugdunum (modern Lyon, France), between the armies of the Roman emperor Septimius Severus and of the Roman usurper Clodius Albinus. Severus' victory finally established him as the sole emperor of the Roman Empire following the Year of the Five Emperors and immediate aftermath.

This battle is said to be the largest, most hard-fought, and bloodiest of all clashes between Roman forces. According to English historian Edward Gibbon, the Roman historian Cassius Dio placed the total number of Roman soldiers engaged for both sides combined at 150,000. Historian Michael Kulikowski states that Severus led the much larger force with the combined legions of Dacia and the Danubian provinces. Historian A. J. Graham supports Gibbon's number of 150,000 soldiers in total, rather than the sometimes cited number of 300,000 in total and therefore 150,000 on each side, which he states to be a commonly accepted mistranslation of Cassius Dio's original language. Graham also analyses the possible forces available to Albinus and states that the numbers on each side could have been roughly equal.