Stillwater Reservoir is a man-made lake located by Beaver River, New York within the Western Adirondacks.

The lake has a large amount of recreational uses including camping, canoeing, boating, fishing, hunting, snowmobiling, and cross-country skiing.

Camping permits and lake information may be obtained from the hamlet of Stillwater at the Forest Ranger Headquarters.

There is a state owned hard surface ramp on Stillwater Road, 28 miles east of Lowville, New York.

[3] the record low temperature for the state of New York of −52 °F (−47 °C) took place at Stillwater Reservoir, and was later tied by Old Forge on February 17, 1979.