William of Poitiers (c. 1020-1090), Norman chronicler, was born at Les Préaux , near Pont-Audemer, and belonged to an influential Norman family. After serving as a soldier he studied at Poitiers, and then returning to Normandy became chaplain to Duke William (William the Conqueror) and archdeacon of Lisieux. He wrote an eulogistic life of the duke, the earlier and concluding parts of which are lost; and Orderic Vitalis, who gives a short biography of him in his Historia ecclesiastica, says that he also wrote verses. William's Gesta Guillelmi II ducs Normannorum, the extant part of which covers the period between 1047 and 1068, is valuable for details of the Conqueror's life, although untrustworthy with regard to affairs in England. According to Freeman, "the work is disfigured by his constant spirit of violent partisanship." It was written between 1071 and 1077, and was used by Orderic Vitalis.

There is a translation of the Gesta Guillelmi into modern English: The Gesta Guillelmi of William of Poitiers (ISBN 0198205538).

William of Poitiers was also the name of one of the children of Henry II of England. See William, Count of Poitiers.