The Tsna (Russian: Цна) is a river in Kuvshinovsky, Ostashkovsky, Firovsky, and Vyshnevolotsky Districts of Tver Oblast of Russia.

It flows into Lake Mstino, which is drained by the Msta and belongs to the drainage basin of the Neva and the Baltic Sea.

The principal tributaries of the Tsna are the Belaya (right)[1] and the Shlina, that flows into the Vyshny Volochyok Reservoir [ru].

The source of the Tsna is located in the Valdai Hills, in Kuvshinovsky District south of the village of Konakovo.

The natural course of the Tsna proceeds to Lake Mstino, which is connected with the reservoir by a canal, however, currently the Vyshny Volochyok Reservoir regulates the discharge between the drainage basins of the Volga (via the Tvertsa) and the Neva (via the Msta, which flows out of Lake Mstino).