Lake Sapsho (Russian: Сапшо́) is a glacial lake. It is the largest lake (3,04 km²) of the national park Smolenskoye Poozyorye (Russian: Смоле́нское Поозё́рье) in Demidovsky District of Smolensk Oblast, Russia. It is situated northeast of Demidov in the northwestern part of the oblast, near the settlement of Przhevalskoye. A famous Russian traveller of the 19th century Nikolai Przhevalsky compared the lake with Lake Baikal in miniature. The lake is a natural monument. It is connected with the Baltic Sea by rivers Sapsha, Vasilyevka, Yelsha, and Daugava. There are 4 big and 2 small islands on the lake. There are a lot of tumuli of the Tushumlin culture by Lake Sapsho. The flora and fauna of the lake are very diverse. Yet in the beginning of the 20th century there was the industrial fishery.