Mannington Township is a Township in Salem County, New Jersey, United States. As of the United States 2000 Census, the township population was 1,559.

Originally named East Fenwick, Mannington is derived from the Indian word Maneto. Mannington Township, New Jersey is a mere 40 square mile area bounded by Upper Penn's Neck (Penns Grove) and Pilesgrove in the North, Salem NJ in the South, South and East by Upper Alloways Creek, and West by Lower Penn's Neck (Penns Grove).

Mannington Township was first mentioned on May 12, 1721. It had been previously known as East Fenwick Township, which was mentioned on September 3, 1679, though the details of its incorporation are unknown. The township was incorporated by an Act of the New Jersey Legislature on February 21, 1798 as one of New Jersey's original group of 104 townships. A portion of the township was taken in 1878 and annexed by Quinton Township.

According to the United States Census Bureau, the township has a total area of 38.4 square miles (99.5 km²), of which, 34.8 square miles (90.1 km²) of it is land and 3.6 square miles (9.4 km²) of it (9.47%) is water. The Salem River flows along the township's northern and western boundaries.

Mannington Township borders Carneys Point Township, Pilesgrove Township, Alloway Township, Quinton Township, Salem, and Pennsville Township.

Additional information on Mannington Township Schools, Salem County Vocational School, and Salem County Special Services School District