Hamburg 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 3,266, a decrease of 11 from the 2010 census count of 3,277, which in turn reflected an increase of 172 from the 3,105 counted in the 2000 census. The United States Census Bureau's Population Estimates Program calculated that the population of Hamburg increased by 65 to 3,331 in 2023.