Pennington is a borough in Mercer County, in the U.S. state of New Jersey. The borough is located at the cross-roads between the Delaware Valley region to the southwest and the Raritan Valley region to the northeast. As of the 2020 United States census, the borough's population was 2,802, its highest decennial count ever and an increase of 217 (+8.4%) from the 2010 census count of 2,585, which in turn had reflected a decline of 111 (−4.1%) from the 2,696 counted in the 2000 census.

Mercer County is a county located in the U.S. state of New Jersey. Its county seat is Trenton, also the state capital, prompting its nickname The Capital County. Mercer County alone constitutes the Trenton–Princeton metropolitan statistical area and is considered part of the New York combined statistical area by the U.S. Census Bureau, but also directly borders the Philadelphia metropolitan area and is included within the Federal Communications Commission's Philadelphia Designated Media Market Area. The county is part of the Central Jersey region of the state.