Constantine II, emperor of Rome, eldest son of Constantine the Great by his second wife Fausta, born at Aries in Gaul, Aug. V, 312 (according to Gibbon in 316), killed near Aquileia, Italy, early in 340. He was named Caesar and consul when still a little child, and in 335 was appointed governor of Gaul, Spain, and Britain. On the death of his father in 337 the empire was divided between his three surviving sons, each of whom received from the senate the title of Augustus; but a kind of supremacy was accorded to Constantine, the eldest, and he is therefore reckoned as a Roman emperor. In the partition Constantine received Constantinople, Gaul, Spain, Britain, and a small part of Africa; Thrace and the countries of the East were allotted to Constantius; and Constans was acknowledged as sovereign of Italy, Africa, and western Illyricum. Constantine became dissatisfied with the division, and demanded from Constans the cession of Africa. This being refused, he crossed the Julian Alps in 340, and invaded Italy. With a few attendants he was drawn into an ambuscade and killed. His body was found in the little river Alsa, and honored with an imperial funeral.

Constans refused to share with Constantius any part of the dominions of Constantine, and thus became master of more than two thirds of the former Roman empire.