Hillsborough Township is a township in Somerset County, New Jersey, United States. The township is centrally located in the Raritan Valley region within the much larger New York Metropolitan Area. As of the 2010 United States Census, the township's population was 38,303, reflecting an increase of 1,669 (+4.6%) from the 36,634 counted in the 2000 Census, which had in turn increased by 7,826 (+27.2%) from the 28,808 counted in the 1990 Census.