Fanwood is a borough in Union County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 7,318 reflecting an increase of 144 from the 7,174 counted in the 2000 Census, which had in turn increased by 59 from the 7,115 counted in the 1990 Census.Fanwood was incorporated as a borough by an act of the New Jersey Legislature on October 2, 1895, from portions of Fanwood Township, based on the results of a referendum held the previous day. The borough was named for Fannie Wood, an author.