Harald "Bluetooth" Gormsson (Old Norse: Haraldr blátǫnn Gormsson, Danish: Harald Blåtand Gormsen) (probably born c. 935) was the son of King Gorm the Old and of Thyra Dannebod. He died in 985 or 986 having ruled as King of Denmark from around 958 and King of Norway for a few years probably around 970. Some sources state that his son Sweyn forcibly deposed him as King.

The Jelling stones
Harald caused the Jelling stones to be erected to honour his parents. Encyclopædia Britannica (Britannica) considers the runic inscriptions as the most well known in Denmark. The biography of Harald Bluetooth is summed up by this runic inscription from the Jelling stones:
"King Harald bade these memorials to be made after Gorm, his father, and Thyra, his mother. The Harald who won the whole of Denmark and Norway and turned the Danes to Christianity."

Denmark's Conversion to Christianity

King Harald Bluetooth's conversion to Christianity is a contested bit of history, not least because medieval writers such as Widukind of Corvey and Adam of Bremen give conflicting accounts of how it came about.
Widukind of Corvey, writing during the lives of King Harald and Otto I, claims that Harald was converted by a "cleric by the name of Poppa" who, when asked by Harald to prove his faith in Christ, carried a "great weight" of iron heated by a fire without being burned.
Adam of Bremen, writing 100 years after King Harald's death in "History of the Archbishops of Hamburg-Bremen", finished in 1076, tells a story of Harald being forcibly converted by Otto I, after a defeat in battle. However, Widukind does not even mention such an event in his contemporary Res gestae saxonicae sive annalium libri tres or "Deeds of the Saxons", which, considering Widukind was at least partly writing to promote Otto I and his family, is damning to Adam of Bremen's claims.
400 years later, the Heimskringla relates that Harald was converted with Earl Haakon, by Otto II ref needed.
A cleric named "Poppa", perhaps the same one, also appears in Adam of Bremen's history, but in connection with Eric of Sweden, who had supposedly conquered Denmark (there is no evidence that this happened anywhere else). The story of this otherwise unknown Poppo or Poppa's miracle and baptism of Harald is also depicted on the gilded altar piece in the Church of Tandrup in Denmark, a detail of which is at the top of this article. The altar itself has been dated to about 1200. Adam of Bremen's claim regarding Otto I and Harald appears to have been inspired by an attempt to manufacture a historical reason for the archbishops of Hamburg-Bremen to claim jurisdiction over Denmark (and thus the rest of Scandinavia); in the 1070s, the Danish King was in Rome asking for Denmark to have its own arch-bishop, and Adam's account of Harald's supposed conversion (and baptism of both him and his "little son" Sweyn, with Otto serving as Sweyn's godfather) is followed by the unambiguous claim that "At that time Denmark on this side of the sea, which is called Jutland by the inhabitants, was divided into three dioceses and subjected to the bishopric of Hamburg."
As noted above, Harald's father, Gorm the Old had died in 958, and had been buried in a mound with many goods, after the pagan practice. The mound was itself from c. 500 BCE, but Harald had it built higher over his father's grave, and added a second mound to the south. Mound-building was a newly revived custom in the tenth century, perceivably as an "appeal to old traditions in the face of Christian customs spreading from Denmark's southern neighbors, the Germans.”
But after his conversion, around the 960s, Harald had his father's body reburied in the church next to the now empty mound, and erected one of the now famous Jelling stones described above.


The rune stone of Harald, quotation writings this side
Harald undoubtedly professed Christianity at that time and contributed to its growth but with limited success in Denmark and Norway.

Reign
During his reign, Harald oversaw the reconstruction not only of the Jelling runic stones but of other projects as well. Some believe that these projects were a way for him to preserve the economic and military control of his country. During that time, ring forts were built in five strategic locations: Trelleborg on Sjælland, Nonnebakken on Fyn, Fyrkat in central Jylland, Aggersborg near Limfjord, and a second Trelleborg near the city of Trelleborg in Scania in present-day Sweden. All five fortresses had similar designs: "perfectly circular with gates opening to the four corners of the earth, and a courtyard divided into four areas which held large houses set in a square pattern." A sixth Trelleborg is located in Borgeby, in Scania in present-day Sweden. This one has been dated to the vicinity of 1000 AD and has a similar design, so it too may have been built by king Harald.


Harald's kingdom (in red) and his vassals and allies (in pink), as set forth in Heimskringla, Knytlinga Saga, and other medieval Scandinavian sources.
He also constructed the oldest known bridge in southern Scandinavia, known as the Ravninge Bridge at Ravninge meadows, which was 5 meters wide and 760 meters long.
While absolute quiet prevailed throughout the interior, he was even able to turn his thoughts to foreign enterprises. Again and again he came to the help of Richard the Fearless of Normandy (in the years 945 and 963), while his son conquered Samland and, after the assassination of King Harald Greycloak of Norway, he also managed to force the people of that country into temporary subjection to himself.
The Norse sagas presents Harald in a rather negative light. He was forced twice to submit to the renegade Swedish prince Styrbjörn the Strong of the Jomsvikings- first by giving Styrbjörn a fleet and his daughter Tyra, the second time by giving up himself as hostage and an additional fleet. Styrbjörn brought this fleet to Uppsala in Sweden in order to claim the throne of Sweden. However, this time Harald broke his oath and fled with his Danes in order to avoid facing the Swedish army at the Battle of the Fýrisvellir.
As a consequence of Harald's army having lost to the Germans in the shadow of Danevirke in 974, he no longer had control of Norway and Germans settled back into the border area between Scandinavia and Germany. The German settlers were driven out of Denmark in 983 by an alliance consisting of Obodrite soldiers and troops loyal to Harald. Soon after, Harald was killed fighting off a rebellion led by his son Swein. He was believed to have died in 986, although there are many other accounts that claim he died in 985.

Marriages and children
1. Gyrid Olafsdottir, probably by 950.
▪ Thyra Haraldsdatter, married Styrbjörn the Strong
▪ Sweyn Forkbeard. Born about 960. Usually given as the son of Harald and Gyrid, though it is said in some of the older sagas that he was an illegitimate son.
▪ Haakon. Born in 961.
▪ Gunhilde. She married Pallig, Jarl and Ealdorman in Devon. They both died in the St. Brice's Day massacre in November 1002.
2. Thora (Tova) the daughter of Mistivir in 970. She raised the Sønder Vissing Runestone after her mother.

▪ Thyra Haraldsdatter, married Styrbjörn the Strong
▪ Sweyn Forkbeard. Born about 960. Usually given as the son of Harald and Gyrid, though it is said in some of the older sagas that he was an illegitimate son.
▪ Haakon. Born in 961.
▪ Gunhilde. She married Pallig, Jarl and Ealdorman in Devon. They both died in the St. Brice's Day massacre in November 1002.