(anc. Sarus, Germ. Son), a river of the Austrian empire, rises in Carniola, near Ladisch, on the eastern slope of the Carnic or Julian Alps; and flows eastward, separating for some distance Carniola from Styria, then traversing Croatia, and finally separating the Austrian Military Frontier from the Turkish provinces of Bosnia and Servia. It falls into the Danube at Belgrade, after a course of 550 miles. Its chief affluents, which all join it from the south, are the Kulpa, at its junction with which it becomes navigable for vessels of 150 tons, the Unna, Verbas, Bosna, Dyina, and Morava. The Save forms an important means of communication to the countries which it waters, and by it their agricultural productions are easily and cheaply conveyed to their proper markets.