William VIII may refer to:
William VIII, Duke of Aquitaine (1025–1086) William VIII of Montpellier (died 1202) William VIII of Jülich, Count of Ravensberg (–1428) William VIII, Marquis of Montferrat (1420–1483) William VIII, Landgrave of Hesse-Kassel (1682–1760)
See also King William (disambiguation) Prince William (disambiguation) List of people with given name William#Royalty and nobility