The North Sea Empire is the name usually given to the historical unified kingdom ruled by Cnut the Great as king of England, Denmark, Norway, and parts of what is now Sweden between 1016 and 1035. It can also be called more specifically the Anglo-Scandinavian Empire. As one historian put it:

When the eleventh century began its fourth decade, Canute was, with the single exception of the Emperor, the most imposing ruler in Latin Christendom. . . . [H]e was lord of four important realms and the overlord of other kingdoms. Though technically Canute was counted among the kings, his position among his fellow-monarchs was truly imperial. Apparently he held in his hands the destinies of two great regions: the British Isles and the Scandinavian peninsulas. His fleet all but controlled two important seas, the North and the Baltic. He had built an Empire.