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 (−0.3%) from the 2010 census count of 3,277, which in turn reflected an increase of 172 (+5.5%) 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 (+2.0%) to 3,331 in 2023.