Frederick IV (Danish: Frederik; 11 October 1671 – 12 October 1730) was the king of Denmark and Norway from 1699 until his death. Frederick was the son of King Christian V of Denmark-Norway and his consort Charlotte Amalie of Hesse-Kassel. On 5 December 1695 at Copenhagen Castle, he married Louise of Mecklenburg-Güstrow, herself a great-great-granddaughter of Frederick II of Denmark. The couple were crowned King and Queen of Denmark-Norway on 25 August 1699 in the Frederiksborg Chapel. During Frederick's rule Copenhagen was struck by two disasters: the plague of 1711, and the great fire of October 1728, which destroyed most of the medieval capital. Although the king had been persuaded by Ole Rømer to introduce the Gregorian calendar in Denmark-Norway in 1700, the astronomer's observations and calculations were among the treasures lost to the fire. For much of Frederick IV's reign Denmark was engaged in the Great Northern War (1700–1721) against Sweden. In spite of the conclusion of the Peace of Travendal in 1700, there was soon a Swedish invasion and threats from Europe's western naval powers. In 1709 Denmark again entered the war encouraged by the Swedish defeat at Poltava. Frederick IV commanded the Danish troops at the battle of Gadebusch in 1712. Although Denmark emerged on the victorious side, she failed to reconquer lost possessions in southern Sweden. The most important result was the destruction of the pro-Swedish Duchy of Holstein-Gottorp, which re-established Denmark's domination in Schleswig-Holstein. Frederick was deemed a man of responsibility and industry — often regarded as the most intelligent of Denmark's absolute monarchs. He seems to have mastered the art of remaining independent of his ministers. Lacking all interest in academic knowledge, he was nevertheless a patron of culture, especially in art and architecture.

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