Hillsborough, frequently spelled Hillsboro, is a town in Hillsborough County, New Hampshire, United States. The population was 6,011 at the 2010 census. The town is home to Fox State Forest and part of Low State Forest.The main village of the town, where 1,976 people resided at the 2010 census, is defined as the Hillsborough census-designated place, and encompasses the main urban area of the town, located along the Contoocook River at the junction of New Hampshire Route 149 with Henniker Street and Main Street. The town also includes the villages of Hillsborough Center, Hillsborough Upper Village, Hillsborough Lower Village, and Emerald Lake Village.