Gustav IV Adolf (November 1, 1778 – February 7, 1837), was King of Sweden from 1792 until his abdication in 1809. He was the son of Gustav III of Sweden and his queen consort Sophie Magdalena, eldest daughter of Frederick V of Denmark and his first wife Louise of Great Britain. He was the last Swedish ruler of Finland.

Gustav Adolf was born in Stockholm. It was rumored that Gustav Adolf was the biological son of the Nobleman, then Baron and later Count Adolf Fredrik Munck af Fulkila, though this has never been established. He was raised under the tutelage of his father and the liberal-minded Nils von Rosenstein. Upon Gustav III's assassination in March 1792, Gustav Adolf succeeded to the throne at the age of 14, under the regency of his uncle, Charles, duke of Södermanland.

In August 1796 his uncle the regent arranged for the young king to visit St. Petersburg to betroth him to Catherine the Great's granddaughter, Grand Duchess Alexandra Pavlovna. However, the whole arrangement foundered on the obstinate refusal of Gustav to allow his destined bride liberty of worship according to the rites of the Russian Orthodox Church — a rebuff which undoubtedly accelerated the death of the Russian empress. Nobody seems to have suspected the possibility at the time that emotional problems might lie at the root of Gustav's abnormal piety.

On the contrary, when he came of age that year, thereby ending the regency, there were many who prematurely congratulated themselves on the fact that Sweden had now no disturbing genius, but an economical, God-fearing, commonplace monarch to deal with.

Gustav Adolf's prompt dismissal of the generally detested Gustaf Adolf Reuterholm, the duke-regent's leading advisor, added still further to his popularity. On October 31, 1797 Gustav married Friederika, granddaughter of Karl Friedrich, Margrave of Baden, a marriage which seemed to threaten war with Russia but for the fanatical hatred of the French republic shared by the Emperor Paul of Russia and Gustav IV Adolf, which served as a bond of union between them. Indeed the king's horror of Jacobinism was morbid in its intensity, and drove him to become increasingly reactionary and to postpone his coronation for some years, so as to avoid calling together a diet. Nonetheless, the disorder of the state finances, largely inherited from Gustav III's Russian war of 1788-92, as well as widespread crop failures in 1798 and 1799, compelled him to summon the estates to Norrköping in March 1800 and on April 3 the same year. When the king encountered serious opposition at the riksdag, he resolved never to call another.

His reign was ill-fated and was to end abruptly. In 1805, he joined the Third Coalition against Napoleon. His campaign went poorly and the French occupied Swedish Pomerania. When his ally, Russia, made peace and concluded an alliance with France at Tilsit in 1807, Sweden and Portugal were left as Great Britain's European allies. In the winter of 1808, Russia invaded Swedish-occupied Finland on the pretext of compelling Sweden to join Napoleon's Continental System. Denmark likewise declared war on Sweden. By early 1809, less than one year, Sweden surrendered all of Finland to Russia, which Emperor Alexander I then established as an autonomous Grand Duchy under his suzerainty.

Gustav Adolf's inept and erratic leadership in diplomacy and war precipitated his deposition through a conspiracy of army officers. On March 13, 1809 seven of the conspirators broke into the royal apartments in the palace, seized the king, and imprisoned him and his family in Gripsholm castle; Duke Charles (Karl) was thereupon persuaded to accept the leadership of a provisional government, which was proclaimed the same day; and a diet, hastily summoned, solemnly approved of the revolution.

On March 29 Gustav IV Adolf, to save the crown for his son, voluntarily abdicated; but on May 19 the Riksdag of the Estates, dominated by the army, declared that not merely Gustav but his whole family had forfeited the throne. On June 5 the duke regent (Gustav's uncle) was proclaimed king under the title of Charles XIII, after accepting a new liberal constitution, which was ratified by the diet the same day. In December Gustav and his family were transported to Germany.

In exile Gustav used several titles, Count Gottorp, Duke of Holstein-Eutin, and finally settled at St. Gallen in Switzerland where he lived in a small hotel in great loneliness and indigence, under the name of Colonel Gustafsson. It was there that he suffered a stroke and died. At the suggestion of King Oscar II of Sweden his body was finally brought to Sweden and interred in the Riddarholmskyrkan.

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In 1797 he had married Frederika Dorothea Wilhelmina of Baden (1781–1826), with whom he had five children:

# Crown Prince Gustav, after 1809 known as Gustaf Gustafsson, Prince of Vasa (November 9, 1799–1877) # Princess Sofia Wilhelmina (May 21, 1801–1865), married Grand Duke Leopold I of Baden # Prince Carl Gustaf, Grand Duke of Finland (December 2, 1802–1805) # Princess Amalia Maria Charlotta (February 22, 1805–1853), unmarried. # Princess Cecilia (June 22, 1807–1844), married August, Grand Duke of Oldenburg.

His son Gustav would serve as an officer in the service of the Habsburgs of Austria, but would never father a son of his own, only a daughter, later Queen Consort Carola of Saxony, wife of Saxony's King Albert I. Sofia Wilhelmina would marry Grand Duke Leopold of Baden, and their grand-daughter Victoria of Baden would marry into the House of Bernadotte, i.e Gustav V of Sweden. By 1812, Gustav Adolf divorced his consort and following this he had several mistresses, among them Maria Schlegel who gave him the son Adolf Gustafsson.

* H. Arnold Barton, Scandinavia in the Revolutionary Era, 1760–1815, 1986, ISBN 0-8166-1392-3. * Sten Carlsson, Gustaf IV Adolf, 1946.