Sullivan is a town in Cheshire County, New Hampshire, United States. The population was 677 at the 2010 census. It includes the villages of East Sullivan and Ellisville.

Named for General John Sullivan and incorporated on September 27, 1787, Sullivan was formed from parts of Gilsum, Keene, Nelson and Stoddard. Farming became the chief occupation. By 1859, the population was 468. In 1867, Sullivan was the first town in New Hampshire to dedicate a monument to its soldiers lost in the Civil War. The monument sits across from the Sullivan Congregational Church.

According to the United States Census Bureau, the town has a total area of 18.7 square miles (48 km²), of which 18.5 sq mi (48 km²) is land and 0.2 sq mi (0.52 km²) is water, comprising 1.02% of the town. It is drained by Ferry Brook, Meetinghouse Brook, Spaulding Brook and Otter Brook. The highest point in Sullivan is the summit of Boynton Hill at 1,739 feet (530 m) above sea level, in the northern part of town.

The town is served by New Hampshire Route 9.

As of the census of 2000, there were 746 people, 282 households, and 208 families residing in the town. The population density was 40.3 people per square mile (15.6/km²). There were 299 housing units at an average density of 16.2 per square mile (6.2/km²). The racial makeup of the town was 98.39% White, 0.13% African American, 0.94% Native American, 0.27% Asian, and 0.27% from two or more races. Hispanic or Latino of any race were 0.40% of the population.

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