National Day of Sweden, marking the end of the Danish-ruled Kalmar Union and the coronation of King Gustav Vasa

National Day of Sweden is the National Day of Sweden, observed annually as a public holiday on 6 June. Prior to 1983, the day was celebrated only as the Swedish Flag Day. It was officially named the Swedish National Day by the parliament of Sweden in 1983, and became a public holiday in 2005. The day is celebrated in honor of the election of Gustav Vasa as King of Sweden in 1523 and of the adoption of the constitutions of 1809 and 1974.

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

Gustav Eriksson Vasa, also known as Gustav I, was King of Sweden from 1523 until his death in 1560. He was previously self-recognised Protector of the Realm (Riksföreståndare) from 1521, during the ongoing Swedish War of Liberation against King Christian II of Denmark, Norway and Sweden. Gustav rose to lead the Swedish War of Liberation following the Stockholm Bloodbath, where his father was executed. Gustav's election as king on 6 June 1523 and his triumphant entry into Stockholm eleven days later marked Sweden's final secession from the Kalmar Union.

June 6 is the 157th day of the year in the Gregorian calendar; 208 days remain until the end of the year.