Crystal Lake is a reservoir in Gardner, Massachusetts, that offers a variety of recreational activities. The Crystal Lake Community Forest, located along the North Central Pathway bike trail near the lake, provides opportunities for hiking, biking, and wildlife viewing. The forest is managed by Mount Grace Land Conservation Trust and the City of Gardner and protects the water quality of the lake and its watershed.

There is access to the lake at Crystal Lake Park, Crystal Lake Cemetery, and the Crystal Lake Water Treatment Facility, all at the south end of the lake.