| Rank: | 20th |
| Ruled: | March 17, 1040-June 8, 1042 |
| Predecessor: | Harold I |
| Date of Birth: | 1018 |
| Place of Birth: | England |
| Wife: | Never married |
| Buried: | Winchester Cathedral |
| Date of Death: | June 8, 1042 |
| Parents: | Canute and Emma |
Harthacanute (sometimes Hardicanute, Hardecanute; Danish Hardeknud, Canute the Hardy) (1018/1019-June 8, 1042), 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 agreed the following year to leave his elder illegitimate half-brother Harold Harefoot in charge of Canute's realm of England.
Harold took the English crown for himself in 1037, but died (1040) as Harthacanute was preparing to invade. During his ensuing two-year reign in England Harthacanute invited Edward the Confessor (Emma's son by Ethelred the Unready) back from exile in Normandy as co-ruler and next in line to the throne. Harthacanute proved a harsh and unpopular ruler. He was unmarried and had no children. He died on June 8, 1042, in London, and was buried at Winchester. Edward assumed the throne on Harthacanute's death, restoring the Saxon royal line for his lifetime.
| Preceded by: Harold I |
List of British monarchs | Succeeded by: Edward the Confessor |
| Preceded by: Canute the Great |
List of Danish monarchs | Succeeded by: Magnus I of Denmark and Norway |