The Vazuza (Russian: Вазу́за) is a river in Novoduginsky and Sychyovsky districts of Smolensk Oblast and Zubtsovsky District of Tver Oblast, Russia, a right tributary of the Volga River. It is 162 kilometres (101 mi) long, and its drainage basin covers 7,120 square kilometres (2,750 sq mi). The lower part of the river has been transformed into Vazuza Reservoir. The towns of Sychyovka and Zubtsov are located on the banks the Vazuza (the latter at its confluence with the Volga). The main tributaries of the Vazuza are the Kasnya River, the Gzhat River (both right), and the Osuga River (left).