Exiled from the Swedish court as a violent young prince, Styrbjörn the Strong did not fade into obscurity. Instead, he carved a path of conquest across the Baltic, eventually seizing command of the Jomsvikings, the most feared warrior brotherhood of the Viking Age, before turning his fleet toward the land that had banished him. According to the sagas, the man who would become known as Styrbjörn was born around the year 950 as the son of King Olaf Björnson, who ruled Sweden alongside his brother, the future King Eric the Victorious. When Olaf died, the young prince was left in his uncle’s care.
At the age of twelve, Styrbjörn stood before Eric and demanded his rightful place as co-ruler. Eric refused, telling the boy to wait until he was sixteen. The years that followed were marked by a temper that could not be contained. After a quarrel in which a courtier struck him across the nose with a drinking horn, Styrbjörn answered with steel and killed the man.
When he came of age, the thing, the ancient assembly of freemen and chieftains, convened to decide his fate. They judged him unworthy of the crown, fearing the fury and violence that defined his character. King Eric, unwilling to keep his nephew within the kingdom, gave him sixty well-provisioned longships and sent him into exile. It was Eric who added the prefix to the prince’s name, dubbing him Styrbjörn for his unruly and quarrelsome nature, a name that would all but replace his birth name of Björn.
Banished from Sweden with his sister Gyrid by his side, Styrbjörn became a scourge upon the Baltic Sea. Leading a host of hardened warriors, he raided coastal lands without mercy, and his name grew heavy with dread. At the age of twenty, he set his sights on a legendary target: the Jomsvikings, an elite brotherhood of warrior mercenaries bound by an iron code and feared across the northern world. The sources differ on how he achieved it, but all agree on the outcome.
According to the Saga of Styrbjörn the Swedish Champion, preserved in the Flateyjarbók manuscript of the 14th century, he declared war against the Jomsvikings, seized their stronghold of Jomsborg from its founder Pálna-Tóki, and took command of the brotherhood himself. Never before had the order bowed to another leader. The Gesta Danorum, or Deeds of the Danes, offers another version, claiming Styrbjörn came humbly before King Harold Bluetooth of Denmark, offering his sister Gyrid in marriage and seeking aid to regain the Swedish throne. Harold accepted the alliance, conquered the fortress of Jólin, believed to be the same as Jomsborg, and granted it to Styrbjörn along with a mighty force.
From there, the prince and his Jomsvikings ruled the seas, said to bring Denmark more power than any army upon land. The Knytlinga Saga presents yet another account, telling how Styrbjörn waged war in the east before arriving in Denmark and capturing King Harold Bluetooth himself after a battle. From that captivity came an alliance, with Harold giving Styrbjörn his daughter Thyra to wife and binding himself in blood and purpose. A poem in the Saga of Styrbjörn recounts the Danish king’s fall, describing how the Lord of Denmark, Harold, had joined the troop of warriors, oppressed by fate and deprived of lands and people.
With the might of the Jomsvikings at his back and newly won Danish allies, Styrbjörn set sail for Sweden at the head of a formidable host of about two hundred longships. When word reached King Eric that the great fleet had entered Lake Mälaren, he swiftly gathered his army at Fyrisvellir, one of Scandinavia’s oldest and most sacred sites. Upon arrival, Styrbjörn found the waters impossible to navigate further. Undeterred, he swore an oath never to leave Sweden, vowing to claim the crown or fall in the attempt.
To seal this vow and the hearts of his men, he ordered his ships set ablaze. Their path was clear: victory or death. As the army advanced toward Uppsala, the Swedes attempted to block their progress in the forest. Styrbjörn threatened to ignite the woods, and faced with such fearsome resolve, the defenders yielded, allowing his forces to pass unopposed.
Preparing for battle on the plains of Fyrisvellir, King Eric devised a cunning stratagem. He ordered cattle to be leashed together, equipped with spears and blades stuck to them, then drove the frenzied beasts toward the Jomsvikings’ ranks. Chaos erupted, but Styrbjörn, a masterful war chieftain, quickly restored order. The battle raged through that day into the next, with neither side claiming victory.
According to the sagas, the night after the battle, Styrbjörn sacrificed to Thor, seeking the thunder god’s favor. Yet a red-bearded stranger appeared in his camp, reciting a skaldic verse that chastised the prince for disturbing him and foretold his doom. Meanwhile, King Eric made his own offering at Odin’s temple, pledging himself to the Allfather for ten years in return for victory. That night, a tall, cloaked man appeared to Eric and gifted him a reed, instructing him to cast it over his enemies, proclaiming, “May Odin have you all.
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At dawn, Eric obeyed. As the reed flew, it transformed into a javelin in midair, soaring over Styrbjörn’s army, who were instantly struck blind. Then from the hillside, an avalanche thundered down, burying the Jomsvikings and Styrbjörn beneath its weight. King Harold and the Danes fled, returning to their ships, and as they departed, a lone spear was seen flying high overhead, an omen or a sign of divine intervention.
Thus perished the berserker prince, once thought favored by the gods. Countless warriors fell beside him, and the legendary Jomsvikings suffered grievous losses. Consequently, Eric earned the name Eric the Victorious, and his son would go on to inherit the throne of Sweden. Styrbjörn’s name gradually faded into the shadows of history.
Yet his name itself spoke to the force of his character: the “Stir” added for his berserker nature and uncontrollable rage, and “the Strong” for his towering size and immense strength in battle. The primary source recounting his deeds is the Saga of Styrbjörn the Swedish Champion, preserved within the Flateyjarbók, a great Icelandic manuscript compiled in the 14th century, some four hundred years after his time. His name echoes through other sagas as well, including the Chronicle of the Kings of Norway, the Deeds of the Danes, the Knytlinga Saga, and others. His appearance across multiple independent sources lends weight to the belief that he was no mere figure of legend, but a real man whose life carved itself into the history of the north.
According to the Saga of King Heidrek the Wise, Styrbjörn traced his bloodline to King Ragnar Lothbrok, one of the greatest heroes of the Viking Age, descended from the god Odin. As a direct descendant, Styrbjörn was believed to carry Odin’s legacy, manifested in his formidable strength and fierce rage. As the great-great-great-great-grandson of Björn Ironside, Styrbjörn possessed a legitimate claim to the Swedish throne. In the 18th century, the Danish historian Jacob Langebek proposed that Styrbjörn and Thyra were the parents of Thorkel Sprakling.
Thor in turn was the father of Ulf the Earl and Gytha, who would go on to marry Godwin, Earl of Wessex, and become the mother of Harold Godwinson, the last Anglo-Saxon king of England. If Langebek’s theory holds true, Styrbjörn would be the great-grandfather of King Harold through Gytha. Meanwhile, through the male line, Styrbjörn’s legacy continued in Ulf the Earl, whose son Sweyn Estridsson rose to the Danish throne as King Sweyn II.
Thus, if this lineage is to be believed, the blood of Styrbjörn the Strong flowed through both English and Danish royalty, his descendants ascending to the thrones of two great kingdoms.