Milford is a town in Hillsborough County, New Hampshire, United States, on the Souhegan River. The population was 16,131 at the 2020 census, up from 15,115 at the 2010 census. It is the retail and manufacturing center of a multi-town area known informally as the Souhegan Valley.

Hillsborough County is the most populous county in the U.S. state of New Hampshire. As of the 2020 census, the population was 422,937, almost one-third the population of the entire state. Its county seats are Manchester and Nashua, the state's two biggest cities. Hillsborough is northern New England's most populous county as well as its most densely populated.