William of Poitiers (Latin: Guillelmus Pictaviensis, French: Guillaume de Poitiers; c. 1020 – 1090) was a Norman priest who served as the chaplain of Duke William II of Normandy (William the Conqueror), for whom he chronicled the Norman conquest of England in his Gesta Willelmi ducis Normannorum et regis Anglorum ("The Deeds of William, Duke of the Normans and King of the English"). He had trained as a soldier before taking holy orders. Source: Wikipedia (en)