Leader of the Britons against the Saxons in the 5th century, was, according to the legends preserved in Gildas and the Historia Brittonum, of Roman extraction. There are signs of the existence of two parties in the national opposition to the invaders, but as Pascent, son of Vortigern, is said by Nennius to have held his dominions in the west by leave of Ambrosius, the Roman element seems to have triumphed. Some measure of success appears to have attended the efforts of Ambrosius, and it has been suggested that Amesbury in Wiltshire is connected with Emrys, the Celtic form of his name.
See Bede, Eccl. Hist. (Plummer), i. 16; Nennius, Hist. Britt. � 31; Gildas, De excidio Brittarum, � 25; J. Rhys, Celtic Britain (1884), pp. 104, 105, 107.