Lawrenceville is an unincorporated community and census-designated place (CDP) within Lawrence Township in Mercer County, in the U.S. state of New Jersey. The community is situated roughly halfway between Princeton and Trenton. Lawrenceville is part of the Trenton–Princeton metropolitan area within the New York combined statistical area; however, the CDP actually is located approximately 15 miles closer to Philadelphia than to New York City, and as with the remainder of Mercer County, lies within the Federal Communications Commission's Philadelphia Designated Market Area. As of the 2020 census, the CDP's population was 3,751, a decrease of 136 (−3.5%) from the 3,887 recorded at the 2010 census, which in turn had reflected a decrease of 194 (−4.8%) from the 4,081 counted in the 2000 census.