(b. c.ad 283),
son of Maximian, was passed over when Diocletian and Maximian abdicated and Galerius and Constantius I succeeded as Augusti (305). On Constantius's death Flavius Valerius Severus became Augustus, but the praetorian guard proclaimed Maxentius as princeps (306). In 307 he took the title Augustus and reconferred this on his father, calling him from retirement to assist him. Severus failed to suppress Maxentius, who had him executed; Galerius invaded Italy but failed against Maxentius, who now controlled all Italy and Africa. Maximian secured an alliance with Constantine in Gaul by giving him the title Augustus and his daughter Fausta in marriage. In 308 Maximian quarrelled with his son, failed to depose him, and fled to Constantine; at Carnuntum Galerius declared Maxentius a public enemy. A revolt in Africa was defeated by Maxentius's praetorian prefect; famine at Rome was averted. Maximian's renewed attempt to become Augustus (310) caused Constantine to sever his alliance with the family and (312) invade Italy. He marched on Rome and defeated Maxentius' forces (said to have been four times as numerous) at Saxa Rubra; Maxentius was drowned near the Mulvian bridge.