Greenwich Township is a township in Warren County, in the U.S. state of New Jersey. As of the 2020 United States census, the township's population was 5,473, a decrease of 239 (−4.2%) from the 2010 census count of 5,712, which in turn reflected an increase of 1,347 (+30.9%) from the 4,365 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.