Northfield is a city in Atlantic County, in the U.S. state of New Jersey. As of the 2020 United States census, the city's population was 8,434, a decrease of 190 (−2.2%) from the 2010 census count of 8,624, which in turn reflected an increase of 899 (+11.6%) from the 7,725 counted in the 2000 census.

Atlantic County is a county located along the Jersey Shore in the U.S. state of New Jersey. As of the 2020 census, the county was the state's 15th-most-populous county, with a population of 274,534, a drop of 15 from the 2010 census count of 274,549. Its county seat is the Mays Landing section of Hamilton Township. The county is part of the South Jersey region of the state.