Galerius (242?–311 A.D.), Roman Emperor in the East, 305–11. His full name was Gaius Galerius Valerius Maximianus. Emperor Diocletian adopted Galerius as his successor in 293. In 303 Galerius persuaded Diocletian to forbid the practice of Christianity, and the persecution of Christians begun by Diocletian was continued after Galerius became an emperor. In 311 he relented, however, and with three co-emperors, he signed an edict giving Christians freedom of worship.