The Tsna is a river in Kuvshinovsky, Ostashkovsky, Firovsky, and Vyshnevolotsky Districts of Tver Oblast of Russia. It is a tributary of Lake Mstino (technically, of Vyshny Volochyok Reservoir) and belongs to the drainage basin of the Neva and the Baltic Sea. It is long, and the area of its basin . The principal tributary of the Tsna is the Belaya River (right). The source of the Tsna is located close to the drainage divide between Neva and Volga (Caspian Sea) drainage basins, and Tsna used to be an important trade route in the Middle Ages. The town of Vyshny Volochyok and the urban-type settlement of Velikooktyabrsky are located on the banks of the Tsna.