Gustaf V was King of Sweden from 1907 until his death in 1950. He was the eldest son of King Oscar II of Sweden and Sophia of Nassau, a half-sister of Adolphe, Grand Duke of Luxembourg. Reigning from the death of his father, Oscar II, in 1907 to his own death 42 years later, he holds the record of being the oldest monarch of Sweden and the third-longest rule, after Magnus IV and Carl XVI Gustaf. He was also the last Swedish monarch to exercise his royal prerogatives, which largely died with him, although they were formally abolished only with the remaking of the Swedish constitution in 1974. He was the first Swedish king since the High Middle Ages not to have a coronation and so never wore the king's crown, a practice that has continued ever since.
Gustaf's early reign saw the rise of parliamentary rule in Sweden although the leadup to World War I induced his dismissal of Liberal Prime Minister Karl Staaff in 1914, replacing him with his own figurehead, Hjalmar Hammarskjöld, the father of Dag Hammarskjöld, for most of the war.