Sussex is a Borough in Sussex County, New Jersey, United States. As of the 2000 United States Census, the borough population was 2,145.
Sussex was incorporated as a borough by an Act of the New Jersey Legislature on October 14, 1891 as Deckertown, from portions of Wantage. The borough was renamed as Sussex on March 2, 1902.
In 2008, Sussex Borough considered consolidation with surrounding Wantage Township.