William FitzWilliam
William FitzWilliam or Fitzwilliam may refer to:
- William Fitzwilliam (Sheriff of London), protégé of Cardinal Wolsey
- William FitzWilliam, 1st Earl of Southampton, English courtier
- William Fitzwilliam (Dean of Wells)
- William Fitzwilliam (died 1559), MP
- William FitzWilliam (Lord Deputy), Lord Deputy of Ireland
- William FitzWilliam, 2nd Baron FitzWilliam, English politician
- William FitzWilliam, 3rd Viscount FitzWilliam, Irish nobleman
- William Fitzwilliam, 3rd Earl Fitzwilliam, British peer
- William Fitzwilliam, 4th Earl Fitzwilliam, British Whig statesman
- William Wentworth-Fitzwilliam, 6th Earl Fitzwilliam, British peer and Liberal politician
- William Wentworth-Fitzwilliam, 7th Earl Fitzwilliam, British Army officer, politician and aristocrat
- William Fitzwilliam, 1st Earl Fitzwilliam, English nobleman, politician, and peer
- William Fitzwilliam, Viscount Milton (d. 1835), British Member of Parliament for Malton (UK [Parliament constituency)|Malton]