Christian II was a Scandinavian monarch under the Kalmar Union who reigned as King of Denmark and Norway, from 1513 until 1523, and Sweden from 1520 until 1521. From 1513 to 1523, he was concurrently Duke of Schleswig and Holstein in joint rule with his uncle Frederick.

The Kalmar Union was a personal union in Scandinavia, agreed at Kalmar in Sweden as designed by widowed Queen Margaret of Norway and Sweden. From 1397 to 1523, it joined under a single monarch the three kingdoms of Denmark, Sweden, and Norway, together with Norway's overseas colonies.