Hudson is a town in Hillsborough County, New Hampshire, United States. The population was 22,928 at the 2000 census. The primary settlement in town, where over 34% of the population resides, is defined as the Hudson census-designated place (CDP) and is located at the junctions of New Hampshire Routes 102, 111 and 3A, directly across the Merrimack River from the city of Nashua.