Cranbury is a township in southern Middlesex County, within the U.S. state of New Jersey. As of the 2020 United States census, the township's population was 3,842, a decrease of 15 (−0.4%) from the 2010 census count of 3,857, which in turn reflected an increase of 630 (+19.5%) from the 3,227 counted in the 2000 census.