Magnus was born in
Norway, either in April or May 1316. His father was Duke
Erik Magnusson, son of King
Magnus Ladulås of Sweden. His mother was
Ingeborg, daughter of King
Haakon V of Norway. Magnus was elected king of Sweden on 8 July 1319 at
Mora Thing to prevent the previous king
Birger Magnusson, his uncle, from returning to power. Magnus was also acknowledged as the
hereditary king of Norway at
Haugating in
Tønsberg in August of the same year. After his mother Ingeborg was removed from the regency in 1322–1323, the countries were ruled by local magnates until Magnus came of age. Magnus was declared to have come of age at 15 in 1331. This provoked resistance in Norway, where a statute from 1302 stipulated that a king came of age at the age of 20, and a rising by
Erling Vidkunsson and other Norwegian nobles ensued. In 1333, the rebels submitted to King Magnus. In 1332 the lands of the eastern Danish provinces, which included
Scania,
Blekinge and
Ven were sold to King Magnus by Duke Johan of Holstein (who had received the provinces from the Danish king), after the local population expressed dissatisfaction with Duke Johan and stated they would rather be ruled by the Swedes. The Duke started negotiations with the Swedes and it was agreed that the Swedish king would redeem the pledge for 34,000 marks of silver (6 432 kilo). When the Danish king refused to recognise King Magnus's ownership of Skåneland, Magnus turned to the Pope, requesting confirmation of the purchase but received only evasive answers. Mainly as a result of his mother's lien on certain castles in Denmark, Magnus waged war with King Valdemar in the
Kalundborg War. Peace between them was concluded in the autumn of 1343 in Varberg, when Valdemar formally renounced all claims to Scania, Blekinge and
Halland. On 21 July 1336, Magnus was crowned king of both Norway and Sweden in
Stockholm. This caused further resentment in Norway, where the nobles and magnates desired a separate Norwegian coronation. A second rising by members of the high nobility of Norway ensued in 1338. In 1335, Magnus married
Blanche, daughter of
John I, Marquis of Namur, and
Marie of Artois, a descendant of
Louis VIII of France. The wedding took place in October or early November 1335, possibly at
Bohus castle. As a wedding gift Blanche received the province of
Tunsberg in Norway and
Lödöse in Sweden as fiefs. They had two sons,
Erik and
Haakon, plus at least two daughters who died in infancy and were buried at
Ås Abbey. Opposition to Magnus' rule in Norway led to a settlement between the king and the Norwegian nobility at
Varberg on 15 August 1343. In violation of the Norwegian laws on royal inheritance, Magnus' younger son, Haakon, would become king of Norway, with Magnus as
regent during his minority. Later the same year, it was declared that Magnus' elder son, Erik, would become king of Sweden on Magnus' death. Thus, the union between Norway and Sweden would be severed. This occurred when Haakon came of age in 1355. Because of the increase in taxes to pay for the acquisition of the Scanian province, some Swedish nobles supported by the Church attempted to oust Magnus, setting up his elder son Erik as king. Erik died supposedly of the
plague in 1359, with his wife
Beatrix and their son. == Peace of Nöteborg ==