High Quality Content by WIKIPEDIA articles! William I (c. 1027 or 1028 ? 9 September 1087), better known as William the Conqueror, was the King of England from Christmas, 1066 until his death. He was also William II, Duke of Normandy, from the 3 July 1035 until his death. Before his conquest of England, he was known as "William the Bastard" (French: Guillaume le Bâtard) because of the illegitimacy of his birth. William was already known as "the Conqueror" prior to 1066 due to his military success in Brittany.