Gustav I, commonly known as Gustav Vasa, was King of Sweden from 1523 until his death in 1560, 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.

The House of Vasa or Wasa was an early modern royal house founded in 1523 in Sweden. Its members ruled the Kingdom of Sweden from 1523 to 1654 and the Polish–Lithuanian Commonwealth from 1587 to 1668; its agnatic line became extinct with the death of King John II Casimir of Poland in 1672.