Sweyn I Forkbeard (Old Norse: Sveinn Tjúguskegg; c. 960 − 3 February 1014) was king of Denmark and England, as well as parts of Norway. His name appears as Swegen in the Anglo-Saxon Chronicle.

He was a Viking leader and the father of Cnut the Great. On his father Harald Bluetooth's death in late 986 or early 987, he became King of Denmark; in 1000, with allegiance of the Trondejarl, Erik of Lade, he was ruler over most of Norway. After a long effort at conquest, and shortly before his death, in 1013 he became the first of the Danish Kings of England.

On the northern edges of the relatively recent Holy Roman Empire, with its roots in Charlemagne's conquests about two hundred years prior to Sweyn's time, Sweyn Forkbeard had coins made with an image in his likeness. The Latin inscription on the coins read, "ZVEN REX DÆNOR", which translates as "Sven, king of Danes".

Sweyn's father, Harald Bluetooth, was the first of the Scandinavian kings to officially accept Christianity, in the early or mid-960s. According to Adam of Bremen, an 11th-century historian, Harald's son Sweyn was baptised Otto, in tribute to the German king Otto I, who was the first Holy Roman Emperor. Forkbeard is never known to have officially made use of this Christian name. He did not use it on the coins he proudly sent forth, and when he was given the English crown by the Witenagemot of Anglo-Saxon nobles, in 1013, he took the crown as king Sweyn.^{[citation needed]}

Sweyn Asleifsson (c. 1115 - 1171) was twelfth century Viking who appeared in the Orkneyinga Saga.

Sweyn (or Sveinn) was born in Caithness in the early twelfth century, to Olaf Hrolfsson and his wife Åsleik. According to the Orkneyinga Saga, he came to prominence when he murdered Earl Paul of Orkney's cup-bearer c. 1134 in a quarrel over a drinking game, and fled to Tiree to take refuge with Holdbodi Hundason.

In 1140, Holdbodi called on Sweyn to join him raiding the coast of Wales, but they were beaten off, Holdbodi withdrawing to the Isle of Man and Sweyn to Lewis. In the early summer of 1141, Sweyn arrived in Man to join Holdbodi, but the Hebridean had been persuaded to join forces with the Norman-Welsh lord Robert who had defeated them in the previous year, and attacked Sweyn. This created a feud between the former friends.

Some years later, after falling out with his own captains (led by his brother-in-law Thorbjorn Thorsteinsson), Sweyn was driven out of Orkney by Rognvald Kali Kolsson, but King David I persuaded them to make peace.

Edmund Ironside or Edmund II (Old English: Eadmund II Isen-Healf; c. 988/993 – 30 November 1016) was king of England from 23 April to 18 October 1016 and of Wessex from 23 April to 30 November 1016. His cognomen "Ironside" is not recorded until 1057, but may have been contemporary. According to the Anglo-Saxon Chronicle, it was given to him "because of his valour" in resisting the Danish invasion led by Cnut the Great. He fought five battles against the Danes, ending in defeat against Cnut on 18 October at the Battle of Assandun, after which they agreed to divide the kingdom, Edmund taking Wessex and Cnut the rest of the country. Edmund died shortly afterwards on 30 November, and Cnut became the king of all England.

Edmund was a signatory to charters from 993. He was the third of the six sons of King Æthelred the Unready and his first wife, Ælfgifu, who was probably the daughter of Earl Thored of Northumbria. His elder brothers were Æthelstan and Egbert (died c. 1005), and younger ones, Eadred, Eadwig and Edgar. His mother died around 1000, after which his father remarried, this time to Emma of Normandy, who had two sons, Edward the Confessor and Alfred.

Harold Godwinson, or Harold II; Old English: Harold Gōdwines sunu (c. 1022 – 14 October 1066) was the last Anglo-Saxon King of England. Harold reigned from 6 January 1066 until his death at the Battle of Hastings on 14 October of that same year, fighting the Norman invaders led by William the Conqueror during the Norman conquest of England. Harold is the first of only three kings of England to have died in warfare; the other two were Richard I and Richard III.

Harold was a son of Godwin, the powerful Earl of Wessex, and his wife Gytha Thorkelsdóttir, whose supposed brother Ulf Jarl was the son-in-law of Sweyn I and the father of Sweyn II of Denmark.

Godwin and Gytha had several children, notably sons Sweyn, Harold, Tostig, Gyrth and Leofwine and a daughter, Edith of Wessex (1029–1075), who became Queen consort of Edward the Confessor.

As a result of his sister's marriage to the king, Godwin's second son, Harold, became Earl of East Anglia in 1045. Harold accompanied his father into exile in 1051, but helped him to regain his position a year later. When Godwin died in 1053, Harold succeeded him as Earl of Wessex (a province at that time covering the southernmost third of England). This arguably made him the most powerful figure in England after the king.