Christian II (1 July 1481 – 25 January 1559) 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.
As king, Christian tried to maintain the Kalmar Union between the Scandinavian countries which brought him to war with Sweden, lasting between 1518 and 1523. Though he captured the country in 1520, the subsequent slaughter of leading Swedish nobility, churchmen, and others, known as the Stockholm Bloodbath, caused the Swedes to rise against his rule. He was deposed in a rebellion led by the nobleman and later king of Sweden Gustav Vasa. He attempted to bring in a radical reform of the Danish state in 1521–22, which would have strengthened the rights of commoners at the expense of the nobles and clergy. The nobility rose against him in 1523, and he was exiled to the Netherlands, ceding the Danish throne to his uncle Frederick. After attempting to reclaim the thrones in 1531, he was arrested and held in captivity for the rest of his life, first in Sønderborg Castle and later at Kalundborg Castle. Supporters tried to restore him to power both during his exile and his imprisonment but they were defeated decisively during the Count's Feud in 1536. Christian died at Kalundborg in 1559.
Christian married Isabella of Austria, granddaughter of Maximilian I, Holy Roman Emperor, in 1515. Isabella died in 1526, after which her family took Christian's three children from him. His relationship with his mistress, Dyveke Sigbritsdatter, pre-dated his marriage and continued until her death in 1517. Christian's persecution of her supposed murderer contributed to his political isolation and downfall. Dyveke's mother, Sigbrit Willoms, became an influential councillor and followed Christian into exile.