Northwood Lake is a long, narrow, shallow lake located in southeastern New Hampshire, in the town of Northwood, Rockingham County. It is situated approximately 18 miles from Concord, and has 2 miles of shoreline along Route 4, the major east-west highway between the capital city area and the state university, the seashore, and the state of Maine. It is a natural lake raised by damming, having an area of 278 hectares, a mean depth of 2.8 meters, and a maximum depth of 7.3 meters.

The lake functions as the final settling basin for several lakes in its 6,226 hectares watershed, prior to its discharge forming the Little Suncook River. The watershed is primarily rural forested and agricultural lands. A large dairy farm and associated corn fields lie along its major tributary Narrows Brook.

Northwood Lake has a free and unencumbered boat launch, a commercial marine, a town beach that is available to non-residents, and a Boy Scout camp. Most of the lake's shoreline is developed, consisting primarily of single family camps and homes. A restaurant and several businesses are located near the lake along Route 4 and a trailer park exists on the shoreline at Northwood Narrows (Q, 3).