William Adelin (1103 – November 25, 1120) was the only legitimate son of Henry I of England and his wife Maud of Scotland. His maternal grandparents were Malcolm III of Scotland and Saint Margaret of Scotland. The second part of William's name is variously referred to as Audelin, Atheling, or Aetheling. In any case it is derived from the Old English Ætheling, meaning "son of the king".
His early death in the White Ship disaster re-arranged the politics of England and France. William initially survived the wreck, made it into a life-boat, but perished trying to rescue his half-sister. Since he was but 17 or 18, he had only limited opportunity for personal influence in the political affairs of his father's domains, principally in two ways.
During his long reign Henry would face several eruptions of hostilities due to the alliances of rival regions with some of his neighbors. As part of an effort to bring Anjou, a long-time rival of Normandy, into his sphere of allegiance, in 1113 Henry betrothed William to Isabella d'Anjou, eldest daughter of Count Fulk V of Anjou. The marriage finally took place in 1119. William's new wife was on another ship at the time of the wreck, and survived him to become a nun and eventually, Abbess of Fontevrault.
The King of France was another of the hostile neighbors. A major item of contention was the ostensible duty for Henry to do homage as Duke of Normandy. As a king in his own right, Henry was loathe to comply and in 1115 he offered to have William do this in his stead. This offer was eventually accepted in 1120, after an intervening period of war and William did homage to Louis VI of France in the middle of 1120. For this reason William is sometimes counted as Duke of Normandy.
These roles paled in importance, however, as his death affected events in the early 12th century significantly. The impact of White Ship disaster was that it left Henry with no male heir. William's older sister Matilda succeeded him as Heir Presumptive, but on Henry's death those barons who had vowed to support her accession to the throne reneged and Stephen, William and Matilda's cousin, seized the throne. His reign was marked by anarchy ulitimately resolved only upon Stephen's death.
William's mother Queen Matilda usually served as Henry's regent in England while he was away in Normandy. After her death in 1118 William was old enough to serve in her stead. He was closely advised in this role by the king's administrators such as Roger of Salisbury. During the last year or so of his life he was sometimes referred to as rex designatus (king designate). Nevertheless William had very little real power.
- Hollister, C. Warren. Henry I (Yale Monarchs Series)