William Wallace Duncan (1839–1908) was an American Bishop of the Methodist Episcopal Church, South, elected in 1886.
He was born 20 December 1839 in Boydton, Virginia, of Scots-Irish descent and of scholarship. He was the son of Professor David Duncan, a native of Ireland, and of University of Edinburgh in Scotland. He settled in Kentucky, then migrated to Virginia.
William graduated from Wofford College in South Carolina in 1858 and joined the Virginia Annual Conference of the M.E. Church, South in 1859. He was a Chaplain of the Army of the Confederate States of America during the American Civil War. Rev. Duncan transferred to the South Carolina Conference in 1875. He was a delegate to the First and Second Ecumenical Methodist Conferences, in 1881 and 1891, respectively. Prior to his election to the Episcopacy, he served as a Pastor and an Educator.
Bishop Duncan died 2 March 1908 in Spartanburg, South Carolina, where he is also buried.
- J. C. Kilgo, An Appreciation, 1908.
- List of Bishops of the United Methodist Church
- Sketch by Bishop Fitzgerald in Fitzgerald, O.P. and Galloway C.B., Eminent Methodists, 1897.
- Leete, Frederick DeLand, Methodist Bishops. Nashville, The Parthenon Press, 1948.