Gustaf V was King of Sweden from 8 December 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 nearly 43 years later, he holds the record of being the oldest monarch of Sweden with the third-longest reign after Magnus IV (1319–1364) and Carl XVI Gustaf (1973–present). 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.

Oscar II was King of Sweden from 1872 until his death in 1907 and King of Norway from 1872 to 1905.