Washington 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 6,492,
The township is one of six municipalities in New Jersey under the name Washington (one of which is a borough, five of which are townships). Washington Township, Warren County completely surrounds the borough of Washington. Mansfield Township, also in Warren County, borders both this municipality and another Washington Township in Morris County.
Washington Township was incorporated as a township by an act of the New Jersey Legislature on April 9, 1849, from portions of Mansfield Township. Portions of the township were taken on February 20, 1868, to create Washington Borough. The township was named for George Washington, one of more than ten communities statewide named for the first president. It is one of five municipalities in the state of New Jersey with the name "Washington Township". Another municipality, Washington Borough, is completely surrounded by Washington Township.
Geography
According to the United States Census Bureau, the township had a total area of 18.05 square miles (46.75 km<sup>2</sup>), including 17.96 square miles (46.52 km<sup>2</sup>) of land and 0.09 square miles (0.23 km<sup>2</sup>) of water (0.49%).
Other unincorporated communities, localities and place names located partially or completely within the township include Bowerstown, Butlers Park, Changewater, Fort Golden, Imlaydale, and Pleasant Valley.
Washington Township borders the municipalities of Franklin Township, Mansfield Township, Oxford Township and White Township in Warren County; and Bethlehem Township, Hampton and Lebanon Township in Hunterdon County. The borough of Washington is completely surrounded by Washington Township, making it part of 21 pairs of "doughnut towns" in the state, where one municipality entirely surrounds another.