King of Denmark from 1035 to 1042 and England from 1040 to 1042. He was the only son of Canute the Great and Emma of Normandy.
He succeeded his father as King of Denmark in 1035, reigning as Canute III, but conflict with Magnus I of Norway prevented him from sailing to England to secure his position there. Consequently, it was agreed that his elder illegitimate
half-brother Harold Harefoot would be regent in charge of England.
Harold took the English crown for himself in 1037—Harthacanute being "forsaken because he was too long in Denmark"—and Harthcanute's mother Emma, who had previously been staying at Winchester with some of Harthacanute's housecarls, fled to Bruges in Flanders. After Harthacanute had settled the situation in Scandinavia through an agreement (in 1038 or 1039) with Magnus in which they agreed that if either of them should die without an heir, the other would be his successor, Harthacanute prepared an invasion of England to depose Harold, arriving at Bruges in 1039. Harold, however, died before an invasion could occur, on March 17, 1040; possibly, if he was known to be ill, Harthcanute had stalled his plans in anticipation of Harold's death. Harthacanute was then invited to England, and he landed at Sandwich on June 17 ("seven days before Midsummer"), with a fleet of 62 warships. He ordered Harold's body thrown into a fen.