Glen Gardner is a borough in Hunterdon County, in the U.S. state of New Jersey. As of the 2020 United States census, the borough's population was 1,682, a decrease of 22 (−1.3%) from the 2010 census count of 1,704, which in turn reflected a decline of 198 (−10.4%) from the 1,902 counted in the 2000 census.

Hunterdon County is a county located in the western section of the U.S. state of New Jersey. At the 2020 census, the county was the state's 18th-most populous county, with a population of 128,947, its highest decennial count ever and an increase of 598 (+0.5%) from the 2010 census count of 128,349, which in turn reflected an increase of 6,360 (5.2%) from the 121,989 counted in the 2000 census. Its county seat is Flemington. The county is part of the Central Jersey region of the state.