Gratianus, Augustus, Roman emperor from 375 to 383, eldest son of Valentinian I., born in Pannonia; at 16, in conjunction with his four-year-old brother, Valentinian II., became ruler over the Western Empire, and three years later found himself, by the death of his uncle Valens, head also of the Eastern Empire, a year after which he summoned Theodosius to be his colleague; his reign is noted for the stern repression of the remains of the heathen worship; in 383, while endeavouring to combat the usurper Maximus, he was captured at Lyons and there put to death (359‒383).
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Gratian * Grattan, Henry