Stewartstown is a town in Coos County, New Hampshire, United States. The population was 1,004 at the 2010 census. It includes the village of West Stewartstown and is part of the Berlin, NH–VT Micropolitan Statistical Area.
Stewartstown was granted in 1770 and incorporated in 1795. Originally named Stuart after Sir John Stuart, it was incorporated as Stewartstown after the Revolutionary War, following the original Scottish spelling of the name.
According to the United States Census Bureau, the town has a total area of 46.8 square miles (121 km2), of which 46.2 square miles (120 km2) is land and 0.6 square miles (1.6 km2) is water, comprising 1.23% of the town. The highest point is the summit of Sugar Hill, at 2,985 feet (910 m) above sea level, near the town's southeastern corner. The 45th parallel north passes through the town.
The primary settlement in the town is the village of West Stewartstown on U.S. Route 3 along the Connecticut River, opposite the town of Canaan, Vermont. Stewartstown village is a mile northeast of West Stewartstown, along Route 3 and opposite the village of Beecher Falls, Vermont. To the east, the village of Stewartstown Hollow is closer to the geographic center of the town, along New Hampshire Route 145.