(c. 1027-87) the king of England from 1066 to 1087. He was the Duke of Normandy, in northern France, when the English king Edward the Confessor died. William claimed that Edward had promised him the right to be the next king of England. He invaded England and defeated King Harold II at the Battle of Hastings in 1066. Later that year he became king. He gave power and land in England to other Normans, and built many castles to control the English people.