King Gustav Vasa was a significant figure in Swedish history, known for founding the modern state of Sweden. He ruled from 1523 to 1560 and is often credited with establishing the Vasa dynasty. His reign marked the end of the Kalmar Union, which had united Sweden, Denmark, and Norway under a single monarch. Gustav Vasa led a successful rebellion against Danish rule, which allowed him to become king. He implemented important reforms, including the establishment of a centralized government and the promotion of the Lutheran Reformation in Sweden, which transformed the country's religious landscape.