* Harold Godwinson: The Anglo-Saxon king of England, Harold, was defeated and killed by William at the Battle of Hastings in 1066.
* Edgar Ætheling: Edgar was the last surviving male member of the Anglo-Saxon royal family and a potential rival for William's throne.
* Gruffydd ap Llywelyn: The ruler of Gwynedd, Gruffydd, led several Welsh uprisings against William's rule.
* Malcolm III of Scotland: Malcolm, king of Scotland, invaded England in support of Edgar Ætheling and was defeated by William at the Battle of Alnwick in 1093.
* Philip I of France: Philip, king of France, supported William's rivals and fought several wars against him.