Andover Township is a township in Sussex County, New Jersey, United States. As of the 2010 United States Census, the township's population was 6,319, reflecting an increase of 286 (+4.7%) from the 6,033 counted in the 2000 Census, which had in turn increased by 595 (+10.9%) from the 5,438 counted in the 1990 Census.
Andover was incorporated as a township by an Act of the New Jersey Legislature on April 11, 1864, from portions of Newton Township, which was split up on that date and dissolved. Portions of the township were taken to form Fredon Township (February 24, 1904) and Andover borough (March 25, 1904). Portions of the township were ceded to Newton town in both 1869 and 1927.
The township was suggestively named after the existing village of Andover, whose name origin is unknown. In the years before World War II, Andover Township was home to Camp Nordland, a retreat and gathering place covering owned and operated by the German American Bund, an American Nazi organization devoted to promoting a favorable view of Nazi Germany. Camp Nordland was shut down by the federal government after Germany declared war on the United States and sold at auction in 1944. The property eventually was acquired by Andover Township and is now called Hillside Park with a recreational hall and sports fields.