William Marmion may refer to:
William Marmion, Baron Marmion of Torrington (died 1265), English clergyman and member of Simon de Montfort's Parliament William Marmion (died 1529) (1461–1529), member of parliament for Gloucester William H. Marmion (1907–2002), bishop of the Episcopal Diocese of Southwestern Virginia William Marmion (politician) (1845–1906), Australian politician
See also Bill Marmion (born 1954), Australian member of the Legislative Assembly of Western Australia