Rhaetia, a province of the Roman empire, which in the reign of Augustus was bounded N. by Vindelicia, E. by Noricum, S. by Gallia Cisalpina, and W. by the country of the Helvetii. Later Vindelicia was added to it, and the province extended as far N. as the Danube. At a still later period it was divided, the original province being called Rhaetia Prima, and Vindelicia, Rhaetia Secunda. Rhaetia proper corresponded to the modern Grisons, Tyrol, and some of the northern parts of Lombardy. The valleys formed by the rivers Athesis (now Adige) and Oenus (Inn) furnished fine lands for cultivation; but the inhabitants were engaged chiefly in the raising of flocks. They were a mountain race, fond of freedom, fighting, and plunder. They were subdued by the Romans under Drusus and Tiberius in 15 B. C., although they fought with desperate courage. Two roads were made through the province, the one leading from Augusta Vindelicorum (Augsburg) to Comum (Como), and the other from the same place to Verona. Their chief city was Tridentum (Trent), and the inhabitants were divided into tribes.

Their descendants in Tyrol speak Romansh, which is a corruption of Latin intermixed with German and Celtic elements, and a number of words of a different origin, considered Etruscan. (See Etruria, and Romansh.) During the latter years of the empire the province became almost depopulated, but after the death of The-odoric it was settled by the Boioarii.