The monarchy of Norway is the system used in Norway by which a hereditary monarch reigns as head of state under a constitutional monarchy with a parliamentary system. The Norwegian monarchy can trace its line back to the reign of Harald Fairhair and the previous petty kingdoms which were united to form Norway; it has been in unions with both Sweden and Denmark for long periods.
The present monarch is King Harald V, who has reigned since 17 January 1991, succeeding his father, Olav V. The heir apparent is his only son, Crown Prince Haakon. The crown prince undertakes various public ceremonial functions, as does the king's wife, Queen Sonja. The crown prince also acts as regent in the king's absence. There are several other members of the royal family, including the king's daughter, grandchildren and sister. Since the dissolution of the union between Norway and Sweden and the subsequent election of a Danish prince as King Haakon VII in 1905, the reigning royal house of Norway has been a branch of the Schleswig-Holstein-Sonderburg-Glücksburg branch of the House of Oldenburg; originally from modern-day Schleswig-Holstein in Germany, agnatically (through Prince Philip) the same royal house as the British (since the accession of Charles III), Danish and former Greek royal families.