Winnisquam Lake is located in Belknap County in the Lakes Region of central New Hampshire, United States, in the communities of Meredith, Laconia, Sanbornton, Belmont, and Tilton. At , it is the fourth-largest lake located entirely in New Hampshire. The lake is primarily fed by the outlet from Lake Winnipesaukee, and Winnisquam's outlet is the Winnipesaukee River, flowing to the Merrimack River. The lake has a maximum depth of .