Manchester is the most populous city in the U.S. state of New Hampshire and the tenth most populous in New England. As of the 2020 census, it had a population of 115,644. Manchester is, along with the city of Nashua, one of two seats of New Hampshire's most populous county, Hillsborough County. Manchester lies near the northern end of the Northeast megalopolis and straddles the banks of the Merrimack River.