Severus (Flavius Valerius Severus), d. 307, Roman emperor (306-7). He participated with Galerius in an unsuccessful attempt to overthrow Maxentius. Surrendering to Maximian (father of Maxentius) at Ravenna on the condition that his life be spared, Severus was taken to Rome. He was later, however, treacherously killed by Maxentius.