Belvidere is a town and the county seat of Warren County, in the U.S. state of New Jersey. As of the 2020 United States census, the town's population was 2,520, a decrease of 161 (−6.0%) from the 2010 census count of 2,681, which in turn reflected a decline of 90 (−3.2%) from the 2,771 counted in the 2000 census.

Warren County is a county located in the U.S. state of New Jersey. According to the 2020 census, the county was the state's 19th-most populous county, with a population of 109,632, its highest decennial count ever and an increase of 940 (+0.9%) from the 2010 census count of 108,692, which in turn reflected an increase of 6,255 (+6.1%) from 102,437 counted at the 2000 census. The county is part of the North Jersey region of the state.