Dover is a city in Strafford County, New Hampshire, United States. The population was 32,741 at the 2020 census, making it the most populous city in the New Hampshire Seacoast region and the fifth most populous city in New Hampshire. It is the county seat of Strafford County, and home to Wentworth-Douglass Hospital, the Woodman Institute Museum, and the Children's Museum of New Hampshire.