Roman emperor in the West, A. D. 350-353. FLAVIUS POPILIUS MAGNENTIUS, according to the accounts preserved by Victor and Zosimus, belonged to one of those German families who were transported across the Rhine, and established in Gaul, about the end of the third century; according to the statement of Julian, which is not irreconcilable with the former, he was a captive taken in war by Constantius Chlorus, or Constantine. Under the latter he served with reputation in many wars, rose eventually to the dignity of count, and was entrusted by Constans with the command of the famous Jovian and Herculian battalions who had replaced the ancient praetorian guards when the empire was remodelled by Diocletian. His ambition was probably first roused by perceiving the frailty of the tenure under wich the weak and indolent prince whom he served held power; and having associated himself with Marcellinus, chancellor of the imperial exchequer (comes sacrarum larqitionum), a plot was deliberately contrived and carefully matured. A great feast was given by Marcellinus at Autun on the 18th of January, A. D. 350, ostensibly to celebrate the birthday of his son, to which the chief officers of the army and the most distinguished of the court were invited. When the night was far spent, Magnentius, who had quitted the apartment under some pretext, suddenly reclad in royal robes, and was instantly saluted as Augustus by the conspirators, whose acclamations were caught up and echoed almost unconsciously by the remainder of the guests. The emissaries despatched to murder Constans succeeded in accomplishing their purpose [CONSTANS, p. 828], the troops no longer hesitated to follow their leaders, the peaceful portion of the population did not resist the example of the soldiery, and thus the authority of the usurper was almost instantly acknowledged throughout Gaul, and quickly extended over all the Western provinces, except Illyria, where Vetranio, the imperial general [VETRANIO], had himself assumed the purple. Intelligence of these events was quickly conveyed to Constantius, who hurried from the frontier of Persia to vindicate the honour of his house, by crushing this double rebellion. The events which followed-the fruitless attempts of the two pretenders to negotiate a peace-the submission of Vetranio at Sardica-the distress of Constantius in Pannonia, which induced him in his turn, but fruitlessly, to make overtures to his opponent-the defeat of Magnentius at the sanguinary battle of Mursa on the Drave, in the autumn of A. D. 351, followed by the loss of Italy, Sicily, Africa, and Spain--his second defeat in the passes of the Cottian Alps--the defection of Gaul--and his death by his own hands about the middle of August, A. D. 353, are fully detailed in other articles. [CONSTANTIUS, p. 847; DECENTIUS, DESIDERIUS, NEPOTIANUS, VETRANIO.]

Magnentius was a man of commanding stature great bodily strength, was well educated, and accomplished, fond of literature, an animated and impressive speaker, a bold soldier, and a skilful general. But, however striking his physical and intellectual advantages, however conspicuous his merits when in a subordinate station, not one spark of virtue relieved the blackness of his career as a sovereign, not one tiait of humanity gave indication that the Christianity which he professed had ever touched his heart. The power which he obtained by treachery and murder he maintained by extortion and cruelty, rendered, if possible, more odious by a hypocritical assumption of good-natured frankness. (Julian. Orat. i. ii.; Liban. Orat. x.; Amm. Marc. 14.5; Aurel. Vict. de Caes. 41, 42, Epit. 41, 42; Eutrop. 10.6, 7; Zosim. 2.41_54; Zonar. 13.5-9; Socrat. H. E. 2.32; Sozomen. H. E. 4.7.)