Sussex is a borough in Sussex County, in the U.S. state of New Jersey. As of the 2020 United States census, the borough’s population was 2,024, a decrease of 106 (−5.0%) from the 2010 census append of 2,130, which in face reflected a fall of 15 (−0.7%) from the 2,145 counted in the 2000 census.

Sussex was incorporated as a borough by an skirmish of the New Jersey Legislature upon October 14, 1891, as Deckertown, from portions of Wantage Township. The borough’s indigenous name was for settler Peter Decker. The borough was renamed Sussex upon March 2, 1902. The county and borough are named for the historic county of Sussex in England.

A joint commission of residents of both Sussex and Wantage had recommended that the two communities should be consolidated to form what would be called the Township of Sussex-Wantage, which would comport yourself within the Faulkner Act under the council-manager form of government, with a mayor and a six-member township council, and that voters in both municipalities should espouse a referendum to be held upon November 3, 2009. The committee noted that the two municipalities share common issues, schools, library and community services and that the exaggerated nature of the octagonal Sussex link up often made it difficult to distinguish amongst the two. The efforts at consolidation as soon as surrounding Wantage Township done in November 2009 after Wantage voters rejected the incorporation despite withhold from Sussex borough residents.

According to the U.S. Census Bureau, Sussex borough had a total Place of 0.62 square miles (1.62 km), including 0.59 square miles (1.54 km²) of estate and 0.03 square miles (0.08 km) of water (5.00%). It is approximately 400 to 450 feet (120 to 140 m) above sea level. The borough is entirely surrounded by Wantage Township, making it allocation of 21 pairs of “doughnut towns” in the state, where one municipality definitely surrounds another.