He was of Illyrian origin; a fictitious connection with the family of Claudius Gothicus was attributed to him by Constantine. Having distinguished himself by his military ability and his able and gentle rule of Dalmatia, he was, on March 1, 293, adopted and appointed Caesar by Maximian, whose step-daughter, Flavia Maximiana Theodora, he had married in 289 after renouncing his wife Helena (the mother of Constantine).
In the distribution of the provinces, Gaul and Britain were allotted to Constantius. In Britain, Carausius and subsequently Allectus had declared themselves independent, and it was not till 296 that, upon the defeat of Allectus, it was re-united with the empire.
In 298 Constantius overthrew the Alamanni in the territory of the Lingones (Langres) and strengthened the Rhine frontier. During the persecution of the Christians in 303 he behaved with great humanity. He obtained the title of Augustus on May 1, 305, and died the following year shortly before the July 25 at Eboracum (York) during an expedition against the Picts and Scots.
This entry was originally from the 1911 Encyclopedia Britannica.
Diocletian (284 - 305),
Maximian (286 - 305)
Constantine the Great