A river of Russia, anciently called the Borysthenes, the third largest for volume of water in Europe, surpassed only by the Danube and the Volga; rises in the province of Smolensk, and flowing in a generally southerly direction, falls into the Black Sea below Kherson after a course of 1330 m.; it traverses some of the finest provinces of the empire, and is navigable nearly its entire length.