Biography of Harald Bluetooth, Former King of Denmark and Norway

Harald Bluetooth

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Harald Bluetooth (c. 910–c. 987), otherwise known as King Harald I of Denmark, was best known for three major achievements. First, he completed the work of unifying Denmark under a single ruler. Second, he conquered Norway—an event which had major historical consequences. Finally, he converted the Danes and Norwegians to Christianity. The dynasty he founded went on to rule over an increasingly large kingdom that, at its height, included much of the British Isles and parts of Sweden.

Fast Facts: Harald Bluetooth

  • Known For: King of Denmark and Norway
  • Also Known As: Haraldr Gormsson, Harald Blåtand Gormsen, Harald I
  • Born: c. 910 in Jelling, Denmark
  • Parents: King Gorm the Old and Thyra Dannebod
  • Died: c. 987, probably in Jormsborg in the northern part of modern Poland
  • Spouse(s): Gunhild, Thora (Tova) the daughter of Mistivir, Gyrid Olafsdottir
  • Children: Thyra Haraldsdatter, Sweyn Forkbeard, Haakon, Gunhilde

Early Life

Harald Bluetooth, or Harold Bluetooth, was born around 910, the son of the first king in a new line of Danish royalty, Gorm the Old. His mother was Thyra, whose father was a nobleman of Sunderjylland (Schleswig). Gorm had established his power base in Jelling, in northern Jutland, and had begun to unify Denmark before his reign was over. Thyra was inclined toward Christianity, so it is possible that young Harald had a favorable view toward the new religion when he was a child, even though his father was an enthusiastic follower of the Norse gods.

So fierce a follower of Wotan was Gorm that when he invaded Friesland in 934, he demolished Christian churches in the process. This was not a wise move; shortly after that he came up against the German king, Henry I (Henry the Fowler); and when Henry defeated Gorm, he forced the Danish king not only to restore those churches but to grant toleration to his Christian subjects. Gorm did what was required of him but died a year later, leaving his kingdom to Harald.

Harald's Reign

Harald set out to continue his father's work of unifying Denmark under one rule, and he succeeded very well. To defend his kingdom, he strengthened existing fortifications and built new ones. The "Trelleborg" ring forts, which are considered among the most important remains of the Viking age, date to his reign. Harald also supported the new policy of toleration for Christians, allowing Bishop Unni of Bremen and Benedictine monks from the Abbey of Corvey to preach the gospel in Jutland. Harald and the bishop developed a cordial working relationship, and although he did not agree to get baptized himself, Harald appears to have supported the spread of Christianity among the Danes.

Once he had established internal peace, Harald was in a position to take an interest in external matters, especially those concerning his blood relatives. His sister, Gunnhild, fled to Harald with her five sons when her husband, King Erik Bloodaxe of Norway, was killed in battle in Northumberland in 954. Harald helped his nephews reclaim territories in Norway from King Hakon. He was met with serious resistance at first and Hakon even succeeded at invading Jutland, but Harald was ultimately victorious when Hakon was killed on the island of Stord.

Harald's Christian nephews took possession of their lands and, led by Harald Greycloak (the eldest nephew), they embarked on a campaign to unify Norway under one rule. Unfortunately, Greycloak and his brothers were somewhat heavy-handed in spreading their faith, breaking up pagan sacrifices and despoiling pagan places of worship. The unrest that resulted made unification an unlikely prospect and Greycloak began to forge alliances with former enemies. This did not sit well with Harald Bluetooth, to whom his nephews owed much for his aid in obtaining their lands, and his concerns were borne out when Greycloak was assassinated, ostensibly by his new allies. Bluetooth took the opportunity to assert his rights over Greycloak's lands and was able to take control of Norway not long after.

In the meantime, Christianity had been making some notable headway in Denmark. The Holy Roman Emperor Otto the Great, who professed a deep devotion to the religion, saw to it that several bishoprics were founded in Jutland under papal authority. Due to conflicting and unsubstantiated sources, it is not clear exactly why this led to war with Harald; it may have something to do with the fact that these actions made the dioceses exempt from taxation by the Danish king, or perhaps it was because it made the territory appear to be under Otto's suzerainty. In any case, war ensued, and the exact outcome is also unclear. Norse sources maintain that Harald and his allies held their ground; German sources relate that Otto broke through the Danevirke and imposed strictures on Harald, including making him accept baptism and evangelize Norway.

Whatever burdens Harald had to deal with as a result of this war, he showed himself to retain considerable clout in the following decade. When Otto's successor and son Otto II was busy fighting in Italy, Harald took advantage of the distraction by sending his son, Svein Forkbeard, against Otto's fortress in Slesvig. Svein captured the fortress and pushed the emperor's forces southward. At the same time, Harald's father-in-law, the king of Wendland, invaded Brandenburg and Holstein and sacked Hamburg. The forces of the emperor were unable to counter these attacks, and so Harald reclaimed control of all of Denmark.


In less than two years, Harald had lost all the gains he had made in Denmark and was seeking refuge in Wendland from his son. Sources are silent as to how this turn of events came to be, but it may have had something to do with Harald's insistence on converting his people to Christianity when there was still a considerable number of pagans among the nobility. Harald was killed in battle against Svein in or around 987; his body was brought back to Denmark and laid to rest in the church at Roskilde.


Harald was by no means the most Christian of medieval kings, but he did receive baptism, and he did do what he could to promote the religion in both Denmark and Norway. He had his father's pagan tomb converted to a Christian place of worship. Although the conversion of the populace to Christianity was not completed in his lifetime, he did allow a fairly robust evangelization to take place.

In addition to constructing the Trelleborg ring forts, Harald extended the Danevirk and left a remarkable runestone in memory of his mother and father in Jelling.

The modern Bluetooth technology used to connect electronic devices was named for the ancient Viking king. According to Jim Kardach, one of the founders of Bluetooth SIG:

“Harald had united Denmark and Christianized the Danes! It occurred to me that this would make a good codename for the program. At this time I also created a PowerPoint foil with a version of the Runic stone where Harald held a cellphone in one hand and a notebook in the other and with a translation of the runes: 'Harald united Denmark and Norway' and 'Harald thinks that mobile PC’s and cellular phones should seamlessly communicate.'"


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Snell, Melissa. "Biography of Harald Bluetooth, Former King of Denmark and Norway." ThoughtCo, Aug. 28, 2020, Snell, Melissa. (2020, August 28). Biography of Harald Bluetooth, Former King of Denmark and Norway. Retrieved from Snell, Melissa. "Biography of Harald Bluetooth, Former King of Denmark and Norway." ThoughtCo. (accessed March 24, 2023).