Flemington is a borough in and the county seat of Hunterdon County, in the U.S. state of New Jersey. Most of the borough is located in the Amwell Valley, a low-lying area of the Newark Basin, and the Raritan Valley, the South Branch of the Raritan River, which flows through the center of Flemington. Northwestern portions of the borough sit on the Hunterdon Plateau. As of the 2020 United States census, the borough's population was 4,876, its highest decennial count ever and an increase of 295 (+6.4%) from the 2010 census count of 4,581, which in turn reflected an increase of 381 (+9.1%) from the 4,200 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.