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 from the 2010 census count of 8,624, which in turn reflected an increase of 899 from the 7,725 counted in the 2000 census. Northfield was founded by Jeremiah Leeds; he has a gravestone at Oxford Circle, but it is not certain that he was buried there.