Coordinates: 43°20′11″N 71°15′44″W / 43.3365°N 71.2621°W The Big River is a 14.9-mile-long (24.0 km)river located in central New Hampshire in the United States. It is a tributary of the Suncook River, part of the Merrimack River (and therefore Gulf of Maine) watershed.
The Big River rises in high ground in the southern corner of Alton, New Hampshire and flows southeast through corners of New Durham and Farmington into Strafford. Running up against the Blue Hills Range, the river reverses course, turning west into Barnstead, where it meets the Suncook River in the village of Center Barnstead.