The Kalmar Union or Union of Kalmaris (Danish, Norwegian and Swedish: Kalmarunionen; Latin: Unio Calmariensis) was a personal union that from 1397 to 1523 joined under a single monarch the three kingdoms of Denmark, Sweden (then including Finland), and Norway, together with Norway’s overseas dependencies (then including Iceland, Greenland, the Faroe Islands and the Northern Isles). The Union was not quite continuous; there were several short interruptions. Legally the countries remained separate sovereign states, but with their domestic and foreign policies being directed by a common monarch.
One main impetus for its formation was to block German expansion northward into the Baltic region. The main reason for its failure to survive was the perpetual struggle between the monarch, who wanted a strong unified state, and the Swedish and Danish nobility which did not. Diverging interests (especially the Swedish nobility‘s dissatisfaction with the dominant role played by Denmark and Holstein) gave rise to a conflict that would hamper the union in several intervals from the 1430s until its definitive breakup in 1523 when Gustav Vasa became king of Sweden.
Norway continued to remain a part of the realm of Denmark–Norway under the Oldenburg dynasty for nearly three centuries until its dissolution in 1814. Then Union between Sweden and Norway lasted until 1905, when a grandson of the incumbent king of Denmark was elected its king, whose direct descendants still reign in Norway.
In 1397, the land area of the union was as large as 3,000,000 square kilometres under the rule of Margaret I of Denmark.
Flag of the Kalmar Union