- November 13: St. Brice's Day Massacre: English king Ethelred the Unready orders all Danes in England killed.
- Ethelred the Unready marries Emma of Normandy, daughter of Richard the Fearless, Duke of Normandy.
- Brian Boru, King of Leinster and Munster, becomes High King of Ireland, breaking the Uí Néill monopoly on the title.
- Henry II succeeds Otto III as king of Germany.
- With a new group of colonists, an epidemic hits the Viking colony in Greenland.
- Danegeld is paid by Ethelred the Unready to prevent Viking raids against England.
- War breaks out between Byzantine Emperor Basil II and Bulgarian tsar Samuil.
- June 21: Pope Leo IX