The River Daugava (in Latvian) or Western Dvina (Russian: Западная Двина́ (Zapadnaya Dvina); Belarusian: Заходняя Дзвіна, [zaˈxodnʲaja dzʲvʲiˈna], traditionally Дзвiна, Dzvina; German: Düna), not to be confused with Northern Dvina, is a river rising in the Valdai Hills, Russia, flowing through Russia, Belarus, and Latvia, draining into the Gulf of Riga in Latvia, an arm of the Baltic Sea. The total length of the river is 1,020 km (630 mi): 325 km in Russian Federation, 328 km in Belarus, and 367 km – in Latvia. In the 19th century, it was connected by a canal to the Berezina and Dnieper rivers (canal is currently not functioning). The Daugava forms part of the international border between Latvia and Belarus.

According to C.Michael Hogan, the Daugava River began experiencing environmental deterioration in the era of Soviet collective agriculture (producing considerable adverse water pollution runoff) and a wave of hydroelectric power projects.

There are three hydroelectric dams on the Daugava River – Rīgas HES just upstream from Riga or 35 km from the mouth of the river, Ķegums HPP another 35 km further up or 70 km from the mouth, and Pļaviņas HPP another 37 km upstream or 107 km from the mouth. A fourth one, Daugavpils HES, has been planned but has faced strong criticism. Belarus currently plans to build several hydroelectric dams on the Belarusian part of Western Dvina.