Sigurd Jonsson (1390s – December 1452) was a Norwegian nobleman, knight and the supreme leader of Norway during two interregnums in the mid-15th century. Background Sigurd Jonsson was born at some point between 1390 and 1400. He was the son of the Swedish nobleman Jon Marteinsson (1340–ca. 1400) and Agnes Sigurdsdotter. Agnes was the great-granddaughter of King Haakon V of Norway, through his illegitimate daughter, Agnes Haakonsdatter (1290–1319) and Havtore Jonsson (1275–1320). Sigurd Jonsson was the grandson and the heir of Sigurd Havtoreson (1315-1392), one of the two sons of Agnes Hakonardottir. At the time of Sigurd's birth, Jon Marteinsson was a resident in Norway and a member of the Norwegian Council of the Realm (riksrådet). Sigurd grew up at the family's estate in Sudreim (modern Sørum), east of Oslo. He had two sisters, Catherine and Ingeborg, and a brother, Magnus, but his brother did not survive to reach maturity. Sigurd therefore inherited his father's estates, and also great landholdings from his mother's relatives. As a direct descendant of the old Norwegian royal family, Sigurd was mentioned as a possible candidate for the Norwegian throne. Sigurd was married to Philippa, daughter of Count Hans of Eberstein who was in the service of King Erik of Pomerania and was apparently a relative of the king. Career Sigurd is first mentioned as a member of the Norwegian Council of the Realm (Rigsrådet) in 1434. In 1436, a peasant rebellion led by Amund Sigurdsson Bolt rebelled against King Erik and his officials, besieging Oslo and Akershus Castle. Amund Sigurdsson belonged the noble Bolt family from Våler in Østfold. The Norwegian nobility remained loyal to King Erik. Sigurd Jonsson helped to enter into a ceasefire with Amund Sigurdsson. In September 1439, King Erik gave Sigurd Jonsson the title of drottsete, under which he was to rule Norway in King Erik's name. Sigurd was at the king's court in Visborg in Gotland when he was appointed and he was at the same time made a knight by King Eric. In 1440, the Norwegian Council of the Realm was compelled to follow the example of Sweden and Denmark, and depose King Eric. Sigurd thus became the ruler of the country, as drottsete, during the interregnum while a new king was sought. Norway followed Denmark and Sweden in electing Christopher of Bavaria as the new king, thus maintaining the union between the three countries. After Christopher's coronation