Sweyn II Estridsson, King of Denmark

by Susan Flantzer
© Unofficial Royalty 2025

Reconstruction of King Sweyn II Estridsson’s head based on the skull in Roskilde Cathedral, now in the National Museum in Copenhagen, Denmark; Credit – Wikipedia

Sweyn II Estridsson reigned as King of Denmark from 1047 to 1076. Born in England, circa 1019, Sweyn II was the son of Ulf Thorgilsson, a Danish nobleman with the title of Jarl, a Viking chieftain, governor and regent of Denmark under Cnut the Great, King of England, Denmark, and Norway. Sweyn II’s mother was Estrid Svendsdatter, the sister of Cnut the Great and the daughter of Sweyn Forkbeard, King of Denmark, Norway, and England and either Sigrid Storråda or Gunhilda of Wenden. The descendants of King Sweyn II of Denmark have reigned in Denmark ever since. One of his descendants, Margaret of Denmark, daughter of King Christian I of Denmark, married James III, King of Scots in 1469, introducing Sweyn II’s bloodline into the Scottish royal house. In 1603, James VI, King of Scots inherited the English throne upon the death of Queen Elizabeth I and reigned in England as King James I. Since that time, all English and British monarchs have been Sweyn II’s descendants. Sweyn had at least one sibling, a brother, Beorn Estridsson, Earl of Huntingdon (circa 1020 – 1049).

Sweyn II spent his childhood in England. At the time of his birth, circa 1019, the House of Denmark reigned in England. His maternal grandfather Sweyn Forkbeard, King of Denmark, Norway, and England, reigned in England from 1013 to 1014 and his maternal uncle Cnut the Great, King of England, Denmark, and Norway, reigned in England from 1016 to 1035.

Sweyn II married twice. Around 1047, he married Gyda Anundsdotter of Sweden, daughter of Anund Jacob, King of Sweden and Gunnhildr Sveinsdóttir. It was a short marriage as Gyda died in 1048, allegedly poisoned by Sweyn’s concubine Thora. Two years later, Sweyn married Gunnhildr Sveinsdóttir, the mother of his first wife Gyda.

Sweyn’s second marriage did not last long. The marriage was considered illegal by the Catholic Church because Sweyn and Gunnhildr were too closely related, either because they were cousins or because Sweyn had been married to Gunnhidr’s daughter, and they were threatened with excommunication.

According to the chronicle “Jerusalem History”, Sweyn the Crusader, the son of the King of Denmark, took part in the First Crusade dying in battle in 1097. Some researchers believe that he was the son of Sweyn II but there is no documentary evidence of the existence of Sweyn the Crusader. Sweyn the Crusader would have been born during Sweyn II’s second marriage and would have been living when Sweyn II died in 1076. It would seem logical that a legitimate son of Sweyn II would have been considered as his successor. However, only his illegitimate sons Harald III, Sweyn II’s successor, and Cnut IV, who succeeded Harald III, were considered.

Sweyn II had many mistresses and fathered at least 20 children. His son from his second marriage who died in the First Crusade was his only legitimate child. Five of his illegitimate sons were later kings.

Illegitimate children of Sweyn II with various concubines:

Sweyn’s uncle Cnut the Great died in 1035. Cnut decreed that any sons of his second marriage to Emma of Normandy should take precedence over the sons of his first marriage to Ælfgifu of Northampton. This meant that Cnut and Emma’s only son Harthacnut was the legitimate heir to England and Denmark. At the time of his father’s death, Harthacnut was in Denmark where he easily succeeded his father as King of Denmark. However, he was unable to come to England because Denmark was under threat of invasion by Norway and Sweden. Because of this, the English council elected Harold Harefoot, Cnut’s son from his first marriage, Regent of England as a temporary measure. He was later proclaimed King of the English.

Harold Harefoot’s rule in England, lasted only five years as he died in 1040, aged about twenty-four. Within months, his half-brother Harthacnut arrived in England with sixty-two warships and ascended the English throne unchallenged. He had Harald Harefoot’s body exhumed, decapitated, and thrown into a swamp but then it was retrieved and thrown in the River Thames. A fisherman pulled Harold Harefoot’s body from the River Thames. It was buried at St. Clement Danes Church in London, originally founded by Danes in the ninth century.

Harthacnut was unmarried and in 1041, he invited his half-brother Edward (the Confessor), the son of Æthelred II the Unready, King of the English and Emma of Normandy, home from his exile in Normandy and made him his heir in England. Sweyn was created a Jarl (earl) in Denmark by Harthacnut. When Harthacunt died in 1042, Sweyn asserted his claims to the Danish and English thrones. However, Edward the Confessor became King of England and Magnus I, King of Norway became King of Denmark. Sweyn entered Magnus’ service and swore an oath of allegiance to him. King Magnus was unmarried and only had one child, an illegitimate daughter. In 1047, the 24-year-old Magnus suddenly died in Denmark. On his deathbed, Magnus named Sweyn his heir in Denmark, and finally Sweyn reigned in Denmark as King Sweyn II.

Perhaps King Sweyn II’s greatest accomplishment was giving the Danish Church, Roman Catholic at that time, a firm and lasting organization by creating a framework for the bishops’ rule. Sweyn brought scholars to Denmark to teach him and his people Latin so they could converse with the rest of Europe on equal terms. The German chronicler Adam of Bremen traveled to Denmark to meet Sweyn and was impressed with his patience and wisdom. Sweyn encouraged the building of churches all over Denmark.

In 1066, William II, Duke of Normandy, known as William the Conqueror, conquered England in 1066, overthrowing Harold II Godwinson, King of England, and becoming King William I of England. King Sweyn II attempted to put England once more under Danish rule. He joined forces with Edgar Ætheling, the grandson of Edmund II Ironside, King of the English and the last remaining heir of the Anglo-Saxon royal house, and sent a force to attack England in 1069. However, after capturing the city of York, Sweyn accepted a payment from King William I of England to desert Edgar, who returned into exile in Scotland. Sweyn made another failed attempt to take over England in 1074 – 1075.

Burial site of Sweyn II Estridsen; Credit By Richard Mortel – Funerary monuments, Roskilde Cathedral CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=69758143

King Sweyn II probably died on April 28, 1076, at his estate in Søderup, Southern Jutland, Denmark. He was interred in the southeastern pier at Roskilde Cathedral in Roskilde, Denmark, the traditional burial site of Danish monarchs  A pier is similar to a column and is designed to support arches. In the photo above, a portrait of Sweyn II Ertridsen on the right marks the pier where he is buried.

Portrait of King Sweyn II that marks his place of burial in Roskilde Cathedral; Credit – Wikipedia

A 2015 study suggested that King Sweyn II may have died of Brugada syndrome, a genetic disorder in which the electrical activity in the heart is abnormal. It increases the risk of abnormal heart rhythms and sudden cardiac death. The study showed that perhaps up to fourteen Danish kings who suddenly died at a relatively young age without being ill possibly died of Brugada Syndrome.

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