Hudson is a town in Hillsborough County, New Hampshire, United States. It is located along the Massachusetts state line. The population was 25,394 at the 2020 census. It is the tenth-largest municipality in the state, by population. The urban center of town, where 7,534 people resided as of the 2020 census, is defined as the Hudson census-designated place and is located at the junctions of New Hampshire routes 102, 111 and 3A, directly across the Merrimack River from the city of Nashua.