Peterborough is a town in Hillsborough County, New Hampshire, United States. The population was 6,418 at the 2020 census. The main village, with 3,090 people at the 2020 census, is a census-designated place and lies along the Contoocook River at the junction of U.S. Route 202 and New Hampshire Route 101. Peterborough is 38 miles west of Manchester and 72 miles northwest of Boston.