GALLIENUS, PUBLIUS LICINIUS EGNATIUS, Ro man emperor from A.D. 260 to 268, son of the emperor Valerian, was born about 218. From 253 to 26o he reigned conjointly with his father, during which time he gave proof of military ability. But when his father was taken prisoner by Shapur I. of Persia, in 26o, Gallienus made no effort to obtain his release, or to with stand the incursions of the invaders who threatened the empire from all sides. He deprived the senators of their military and provincial commands, which were transferred to equites. During his reign the empire was ravaged by a pestilence, and the chief cities of Greece were sacked by the Goths. His generals rebelled against him in almost every province of the empire, and this period of Roman history came to be called the reign of the Thirty Tyrants. Gallienus was killed at Mediolanum by his own soldiers while besieging Aureolus, who was proclaimed emperor by the Illyrian legions. His sons Valerianus and Saloninus predeceased him.