William Wallace Duncan (December 20, 1839 – March 2, 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. Bishop Duncan died 2 March 1908 in Spartanburg, South Carolina, where he is also buried.