son of Donnus, was king of several Ligurian tribes in those parts of the Alps, which were called after him, the Cottian Alps. He maintained his independence when the other Alpine tribes were subdued by Augustus, till at length the emperor purchased his submission, by granting him the sovereignty over twelve of these tribes, with the title of Praefectus. Cottius thereupon made roads over the Alps, and shewed his gratitude to Augustus by erecting (B. C. 8) at Segusio, now Suza, a triumphal arch to his honour, which is extant at the present day, and bears an inscription, in which the praefect is called M. Julius Cottius, and the names of the people are enumerated, of which he was praefect. His authority was transmitted to his son, who also bore the name of M. Julius Cottius, and upon whom the emperor Claudius conferred the title of king. But upon the death of this prince, his kingdom was reduced by Nero into the form of a Roman province. (Amm. Marc. 15.10; Strab. iv. p.204; Plin. Nat. 3.20. s. 24; Orelli, Inscr. No. 626; Dion. Cass. 60.24; Suet. Nero 18; Aur. Vict. Caes. 5, Epit. 5; Eutrop. 7.14.)