Exeter is a town in Rockingham County, New Hampshire, United States. Its population was 16,049 at the 2020 census, up from 14,306 at the 2010 census. Exeter was the county seat until 1997, when county offices were moved to neighboring Brentwood. Home to Phillips Exeter Academy, a private university-preparatory boarding school, Exeter is situated where the Exeter River becomes the tidal Squamscott River.