William Duff may refer to:
William Duff, 1st Earl Fife (1696–1763), Scottish peer William Duff (cricketer) (1890–1953), South African soldier and cricketer William Duff (writer) (1732–1815), historically influential Scottish writer on genius and creativity William E. Duff, author William J. Duff (1856–1922), American football player William Duff (Canadian politician) (1872–1953), merchant and politician in Nova Scotia, Canada William Duff (Newfoundland politician) (1842–1913), Newfoundland merchant and politician William Duff (dentist) (born 1962), Scottish dentist Willie Duff (1935–2004), Scottish footballer William Duff (Arabist) (1922–2014) Scottish Arabist and banker, known to be one of the architects of modern Dubai Bill Duff (born 1974), NFL footballer