The Great Sacandaga Lake (formerly the Sacandaga Reservoir) is a large lake situated in the Adirondack Park in northern New York in the United States. The lake has a surface area of about 41.7 square miles (108 km2) at capacity, and the length is about 29 miles (47 km).

The word Sacandaga means "Land of the Waving Grass" in the local native language. The lake is located in the northern parts of Fulton County and Saratoga County near the southern border of the Adirondack Park. A small portion also extends northward into southern Hamilton County.