Back Lake is a 348 acre water body located in Coos County in northern New Hampshire, United States, in the town of Pittsburg. It is part of the Connecticut River watershed. It is situated north of Lake Francis and west of First Connecticut Lake. U.S. Route 3 passes by Back Lake's eastern shore. The lake is classified as a coldwater fishery, with observed species including brook trout, rainbow trout, brown trout, and brown bullhead. There are numerous cabins around the lake, and two public boat launch locations. Boats on the lake are generally restricted to a maximum speed of 10 mph, and skicraft have been banned since 2004.