Canute, the son of Sweyn Forkbeard, accompanied his father on the Danish invasion of England. After his father's death (1014) he began a struggle with Ethelred the Unready and Edmund Ironside for the English throne. He defeated Edmund in 1016 at the Battle of Assandun, secured Mercia and Northumbria, and became King of all England after Edmund's death.

In 1017 he married Emma of Normandy, the widow of Ethelred. In 1018 or 1019 he succeeded to the throne of Denmark and was forced to lead several expeditions to assert his rights there and in the Danish provinces in Norway. In 1028, after an uprising had expelled Olaf II of Norway, Canute was recognized as ruler of that kingdom.

Canute strove to continue English traditions by restoring the church to high place and codifying English law; he also attempted to reconcile Nordic and Christian culture. He gave England peace, and established friendly relations with the Holy Roman Empire and attended the coronation of Conrad II in Rome in 1027.