William Duff
William Duff may refer to:
- William Duff, 1st Earl Fife, Scottish peer
- William Duff (cricketer), South African soldier and cricketer
- William Duff (writer), historically influential Scottish writer on genius and creativity
- William E. Duff, author
- William J. Duff, American football player
- William Duff (Canadian politician), merchant and politician in Nova Scotia, Canada
- William Duff (Newfoundland politician), Newfoundland merchant and politician
- William Duff (dentist), Scottish dentist
- Willie Duff, Scottish footballer
- William Duff (Arabist) Scottish Arabist and banker, known to be one of the architects of modern Dubai
- Bill Duff, NFL footballer