Hudson is a town in Hillsborough County, New Hampshire, United States. It is located along the Massachusetts state line. The population was 24,467 at the 2010 census, with an estimated population of 24,645 in 2013. It is the ninth-largest municipality in the state, by population.The primary settlement in town, where 7,336 people resided at the 2010 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.