Raritan Township is a township in Hunterdon County, New Jersey, United States. As of the 2010 United States Census, the township's population was 22,185, reflecting an increase of 2,376 (+12.0%) from the 19,809 counted in the 2000 Census, which had in turn increased by 4,193 (+26.9%) from the 15,616 counted in the 1990 Census. The southeast part of the township is in the Amwell Valley, while the northwestern part is on the Hunterdon Plateau.
Raritan was incorporated as a township by an Act of the New Jersey Legislature on April 2, 1838, from portions of the now-defunct Amwell Township. Flemington was formed within the township on March 14, 1870, and became an independent borough on April 7, 1910. Portions of the township were ceded to East Amwell Township in 1854 and 1897.