Lake Sterzh (Стерж) is the third largest among the Valdai Lakes in Tver Oblast of Russia. It is the first lake through which the Volga flows. The lake's length is 12 kilometres (7.5 mi), its width is up to 1,500 metres (4,900 ft), and the average depth is 5 metres (16 ft). The area of the lake is 17.9 square kilometres (6.9 sq mi).