William Chauncy Langdon

William Chauncy Langdon (August 19, 1831 in Burlington, Vermont –1895) was a Protestant Episcopal clergyman and a prominent American proponent of the YMCA. He left a career in patent law to help found the YMCA in Washington, DC, the first chapter in a large urban area. He went on to found the National Confederation of Young Men's Christian Associations and was elected its first general secretary in 1854.

He founded three Episcopal Churches in Europe: Grace Church in Rome, 1859 (later renamed as St. Paul's Within the Walls); St James's in Florence, c. 1870; and Emmanuel Church, Geneva, 1873. They are now parishes of the Convocation of Episcopal Churches in Europe.

His son Courtney Langdon (1861-1924) was a poet, professor, and translator of Dante. Another son, William Chauncy Langdon (1871–1947), was a writer, historian, and wrote and produced many historical pageants.