Adeliza (c 1055? - c1066? or prior to 1113) was the (presumed eldest) daughter of William I of England. There is considerable uncertainty about her life, including dates of birth and death.
Orderic Vitalis, who extended William of Jumièges' Gesta Normannorum Ducum (Deeds of the Norman Dukes), states that ‘Adelidis', a daughter of William I, was betrothed to Harold Godwinson - the Harold II who was killed at the Battle of Hastings - and remained single after his death.
However Orderic, in the later books of his Historia Ecclesiastica, also states that she took the veil, but makes her sister Agatha the betrothed of Harold. According to the Oxford Dictionary of National Biography, Orderic places Adeliza as "a virgin under the protection of Roger de Beaumont" which, in the estimation of author Elisabeth van Houts, places her as a nun of St Léger at Préaux, and from this and with reference to the mortuary roll of that convent, deduces that she died prior to 1113.