Littleton is a town in Grafton County, New Hampshire, United States. The population was 5,845 at the 2000 census. Situated at the edge of the White Mountains, Littleton is bounded on the northwest by the Connecticut River. The primary settlement in town, where over 75% of the population resides, is defined as the Littleton census-designated place (CDP), and is centered around the intersection of U.S. Route 302 with New Hampshire Route 116, along the Ammonoosuc River.