Galerius (Latin: Gaius Galerius Valerius Maximianus Augustus; c. 260 – April or May 311), is Roman Emperor from 305 to 311.

During his reign he campaigns, aided by Diocletian, against the Sassanid Empire, sacking their capital Ctesiphon in 299.

He also campaigns across the Danube against the Carpi, defeating them in 297 and 300.

Although he is a staunch opponent of Christianity, Galerius ends the Diocletianic Persecution when he issues an edict of toleration in 311.