Princeton Township is a now-defunct township that was located in Mercer County, New Jersey, United States, from 1838 until it was dissolved after it was merged with Princeton Borough in 2013 to form Princeton, New Jersey. As of the 2010 United States Census, the township's population was 16,265, reflecting an increase of 238 (+1.5%) from the 16,027 counted in the 2000 Census, which had in turn increased by 2,829 (+21.4%) from the 13,198 counted in the 1990 Census.
Princeton was incorporated as a township by an Act of the New Jersey Legislature on April 9, 1838, from portions of West Windsor Township in Mercer County and Montgomery Township in Somerset County. The Borough of Princeton — created on February 11, 1813 within the area that later became Princeton Township — became a fully independent municipality circa 1894. Portions of territory were ceded to the Borough of Princeton on January 4, 1928 and August 21, 1951. On November 8, 2011, voters in Princeton Township voted to consolidate with Princeton Borough, a change that took effect on January 1, 2013.
The Institute for Advanced Study, a private research institution that has been an academic home to Albert Einstein, Kurt Gödel, and many other famous and prize-winning scientists, is located in the former township. Princeton University is located mostly within the former borough, but parts of the campus extended into what was Princeton Township.
The last day Princeton Township existed as an independent municipality was December 31, 2012.