Seliger (Russian: Селиге́р) is a lake in Ostashkovsky District of Tver Oblast and, in the extreme northern part, in Demyansky District of Novgorod Oblast of Russia, in the northwest of the Valdai Hills, a part of the Volga basin. It has the absolute height of 205 metres, the area of 212 square kilometres, and the average depth of 5.8 metres.
Lake Seliger is a large system of lakes linked by effluents, has many small islands and is surrounded by forests, including pine woods with many berries and mushrooms. It is one of the biggest natural lakes of Central Russia. The only outflow of the lake, the Selizharovka River, originates at the southern end of the lake and drains into the Volga after 36 kilometres.
