Alton is a town in Belknap County, New Hampshire, United States. The population was 5,250 at the 2010 census. It is home to Alton Bay State Forest and Mount Major State Forest.
The primary settlement in town, where 501 people resided at the 2010 census, is defined by the U.S. Census Bureau as the Alton census-designated place (CDP) and is centered on the intersection of New Hampshire Route 11 and New Hampshire Route 140. The town also includes the village of Alton Bay, a long-time resort located beside Lake Winnipesaukee.
Originally called "New Durham Gore" because of rocky upland areas, or "gores", the town was settled in 1770, mainly by farmers because the highland areas provided less frost. Merchants then filled the lowlands. Early Alton history recounts stories of the merchants trying to convince the farmers to incorporate. They would succeed on 15 January 1796, when the community was named after Alton, a small market town in Hampshire, England.
Alton was part of Strafford County until Belknap County was erected on 22 December 1840. By 1840, the village of Alton existed at the town's center.