William Fiennes
William Fiennes is the name of the following people:
- William Fiennes, 2nd Baron Saye and Sele (1428–1471), English nobleman
- William Fiennes, 1st Viscount Saye and Sele (1582–1662), English politician
- William Fiennes, 3rd Viscount Saye and Sele (around 1641–1698), English nobleman
- William Fiennes (writer) (* 1970), British literary critic and writer