Sussex is a Borough in Sussex County, New Jersey, United States. As of the United States 2000 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. Sussex Borough is currently planning a consolidation study with surrounding Wantage Township. Nearby Montague Township may also take part in the study.