Charles XII, (born June 17, 1682, Stockholm—died Nov. 30, 1718, Fredrikshald, Nor.), king of Sweden (1697–1718), an absolute monarch who defended his country for 18 years during the Great Northern War and promoted significant domestic reforms. He launched a disastrous invasion of Russia (1707–09), resulting in the complete collapse of the Swedish armies and the loss of Sweden’s status as a great power. He was, however, also a ruler of the early Enlightenment era, promoting domestic reforms of significance.