|King of Viken|
|Reign||26th March, 1140 - 12th January, 1174|
|Spouse||Helena of Gothenland|
|Issue|| Niels II Knudsen|
|Father||Magnus II Nielsen|
|Mother||Adela of Anglia|
|Died|| 12th January, 1174 |
Cnut III was the eldest son of Magnus II and ruler of Viken after his father's death. He also aspired to the thrones of Svealand and Denmark however was not in a real position to challenge for either.
Magnus had been deposed as king of Svealand in 1130 and had been at loggerheads with his successor, Sverker, for many years. To smooth relations between the two kings Cnut was betrothed to Sverker's daughter Helena and the marriage contract was honoured after Magnus's death when Cnut was at a more appropriate age. They would have one son, Niels. There were however several other illegitimate children with concubines.
Sverker seems to have taken Cnut under his wing, indeed; as Cnut and Helena's marriage came with the return of substantial Svealandic estates belonging to Cnut's grandmother, Sverker often required Cnut's leverage and support to rule effectively. He was not above putting him in his place however, as in 1146 when the Danish throne became disputed. Cnut threw his weight behind an attempted invasion to oppose Cnut Lavard however, Sverker was friends with Cnut Lavard and hostile to a united Denmark-Viken. As such the Gothenlandic army was put at Cnut Lavard's disposal to stop Cnut III. He remained largely hostile to Cnut V Lavard and his son Valdemar I (supporting Valdemar's Harald Emune) and spent much of his trying to build a cordon around Denmark, marrying off his illegitimate children in Rugia and Germany.
After Sverker's death Gothenland passed to his son Karl I succeeded him and continued to oppose Cnut III's machinations southwards. However Svealand fell into a period of civil war as the House of Eric attempted to re-cement their rule. As a major landowner, and with his own claim to the throne, Cnut was heavily involved in the politics. He appears to have supported Eric VI's reign and certainly campaigned in Finland with him. After his death however it appeared to come down to a struggle between Magnus II Hendriksson and Burislev Sverkersson. Eager not to have the Sverker clan control both kingdoms again Cnut invaded in 1162 shortly before Magnus's death. Burilsev however defeated Cnut on the battlefield and 'chased him back to Oslo'. Cnut remained commited to idea of seizing the Svealandic throne and, outliving both Burislev and his nephew Kol, would often forment trouble. However this only seemed to strenghten the hand of another challenger, Eric VI's son Cnut.
On Cnut III's death in 1174 Niels succeeded. He in turn would die in 1185 leaving no heirs. Finally, eager to repair relations with Denmark, the nobles of Viken elected Cnut's last surviving child, the illegitimate Hildegard of Rugia as Queen. Viken was moving into Denmark's orbit.