Sapsho, Protected lake in Demidovsky District, Russia.

Lake Sapsho covers approximately 3 square kilometers and sits within Smolenskoye Poozerye National Park, containing six islands of varying sizes. The water reaches depths of nearly 19 meters in its deepest spots.

Neolithic traces dating to the 4th–3rd millennium BC were found on Chernetsky Island and the eastern shore, alongside burial mounds of the Tushemlya and long-barrow cultures. In the 19th century Nikolay Przhevalsky bought the western part of the lake, and the boundary of his estate ran along the esker called Chertova Gryada. The lake is now a nature monument within Smolenskoye Poozerye National Park.

The lake's name is linked to the Sapsha river, and its islands carry folk names: Chernetsky recalls a hermit called Chernets, while Dubovy is also called Island of Love. Since the early 20th century commercial fishing has been banned, and today the lake is used for recreation and small-scale fishing.

The water is warmest and best for swimming from late June through early August when temperatures are comfortable. Visitors should follow park rules carefully and avoid leaving any litter behind.

The six islands in the lake were shaped by glacial erosion from thousands of years ago, making them visible remnants of the ice age in this region. Some islands like Chernetsky are particularly notable for their distinct geological formations.