Margaret of Denmark (1353–1412)

Danish ruler, and Queen of Denmark, Norway, and Sweden. She became Queen of Norway in 1380, Queen of Denmark in 1387 and soon afterwards Queen of Sweden. This union of the three kingdoms was formally recognized in the Treaty of Kalmar (1397).

She was the daughter of Waldemar IV of Denmark. At the age of 10 she was married to King Haakon VI of Norway, whose death in 1380 led to her assuming the crown. She arranged her son Olaf's election as king of Denmark and when he died in 1387 she secured the throne of Denmark. Shortly afterwards she defeated Albert of Mecklenburg, the Swedish king, and obtained possession of the throne of Sweden.