Christian I (February 1426 – 21 May 1481) was a German noble and Scandinavian monarch under the Kalmar Union. He was king of Denmark (1448–1481), Norway (1450–1481) and Sweden (1457–1464). From 1460 to 1481, he was also duke of Schleswig (within Denmark) and count (after 1474, duke) of Holstein (within the Holy Roman Empire). He was the first king of the House of Oldenburg.
In the power vacuum that arose following the death of King Christopher of Bavaria (1416–1448) without a direct heir, Sweden elected Charles VIII of Sweden (1408–1470) king with the intent to reestablish the union under a Swedish king. Charles was elected king of Norway in the following year. However the counts of Holstein made the Danish Privy Council appoint Christian as king of Denmark. His subsequent accessions to the thrones of Norway (in 1450) and Sweden (in 1457) restored the unity of the Kalmar Union for a short period. In 1463, Sweden broke away from the union and Christian's attempt at a reconquest resulted in his defeat by the Swedish regent Sten Sture the Elder at the Battle of Brunkeberg in 1471.
In 1460, following the death of his uncle, Duke Adolphus of Schleswig, Count of Holstein, Christian also became Duke of Schleswig and Count of Holstein.