The Viking-age dynasty of Gorm the Old that unified Denmark, converted it to Christianity, and under Cnut the Great ruled a North Sea empire including England.
The dynasty is named for its seat at Jelling in Jutland, where the first securely historical king, Gorm the Old, ruled in the early tenth century. His son Harald Bluetooth raised the great Jelling runestone claiming to have "won all Denmark for himself" and to have made the Danes Christian — the founding monument of the Danish kingdom.
Harald’s reign brought royal power, a network of ring fortresses, and the conversion that tied Denmark to Latin Christendom, though old Norse religion and Viking raiding continued.
Harald’s son Sweyn Forkbeard turned Danish power outward, raiding England for years and finally conquering it in 1013, driving out King Æthelred the Unready. Sweyn died months later in 1014, and his son Cnut had to win the kingdom again, defeating Edmund Ironside and becoming king of England in 1016.
The Jelling kings thus achieved what generations of Vikings had only raided for: the throne of England itself.
Cnut the Great ruled England, Denmark, and for a time Norway as a single North Sea empire, governing England through English earls and law while drawing on Scandinavian military power. He made a celebrated pilgrimage to Rome in 1027 and presented himself as a Christian European king rather than a Viking raider.
The famous story of Cnut commanding the tide — usually misremembered — was told to show his humility before God, not his arrogance: he set his throne at the sea’s edge to prove that even a king’s power had limits.
Cnut’s empire depended on his own person and did not survive his death in 1035. His sons Harold Harefoot and Harthacnut divided and disputed the inheritance, and both died young and without heirs — Harthacnut in 1042.
The English throne then returned to the West Saxon line under Edward the Confessor, while in Denmark the crown passed to Cnut’s nephew Sweyn Estridsson, founder of the House of Estridsen.
The Jelling dynasty made Denmark a Christian kingdom and, for a generation, the centre of a North Sea empire that placed a Danish king on the English throne. Its monuments at Jelling remain the oldest royal record of the Danish state.
Its brief mastery of England left a lasting mark on English law, land-holding, and the Anglo-Scandinavian character of eleventh-century England, and set the stage for the succession crisis of 1066.