Constantius I. Flavius Valerius, surnamed Chlorus ( ὁ Χλωρός , "the pale"), Roman emperor, A.D. 305, 306, father of Constantine the Great, son of Eutropius, of a noble Dardanian family, by Claudia, daughter of Crispus, brother of the emperors Claudius II. and Quintilius. Born c. a.d. 250. Distinguished by ability, valour, and virtue, Constantius became governor of Dalmatia under the emperor Carus, who was prevented by death from making him his successor. Diocletian (emperor, a.d. 284–305), to lighten the cares of empire, associated Maximian with himself; and arranged that each emperor should appoint a co-regent Caesar. Constantius was thus adopted by Maximian, and Galerius by Diocletian, (Mark 1, a.d. 292). Each being obliged to repudiate his wife and marry the daughter of his adopted father, Constantius separated from Helena, the daughter of an innkeeper, who was not his legal wife but was mother of Constantine the Great, and married Theodore, stepdaughter of Maximian, by whom he had six children. As his share of the empire, Constantius received the provinces Gaul, Spain, and Britain. In a.d. 296 he reunited Britain to the empire, after the rebellion of Carausius, and an independence of ten years. In a.d. 305, after the abdication of Diocletian and Maximian, Galerius and Constantius became Augusti, and ruled together. As the health of Constantius began to fail, he sent for his son Constantine, who was already exceedingly popular, and who was jealously kept by Galerius at his own court. Constantine escaped, and arrived at his father's camp at Gessoriacum (Boulogne-sur-Mer) before embarking on another expedition to Britain. In a.d. 306 Constantius died in the imperial palace at Eboracum (York). He is described as one of the most excellent characters among the later Romans. He took the keenest interest in the welfare of his people, and limited his personal expenses to the verge of affectation, declaring that "his most valued treasure was in the hearts of his people." The Gauls delighted to contrast his gentleness and moderation with the haughty sternness of Galerius. His internal administration was as honourable as his success in war. The Christians always praised his tolerance and impartiality. Theophanes calls him Χριστιανόφρων , a man of Christian principles. He had Christians at his court. Although a pagan, he disapproved of the persecution of Diocletian, and contented himself by closing a few churches and overthrowing some dilapidated buildings, respecting (as the author of the de Morte Persecutorum says) the true temple of God. Christianity spread in Gaul under his peaceful rule, and at the end of the 4th cent. that province had more than 20 bishops. Eutrop. ix.; Aurel. Vict. Caes. 39, etc.; Theoph. pp. 4–8, ed. Paris; Eus. Vit. Const. i. 13–21; Lactantius, de Morte Persecutorum, 15; Smith, D. of G. and R. Biog.; Ceillier, iii. 48, 140, 579.
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