John VI (Portuguese: João VI), nicknamed "the Clement", was King of the United Kingdom of Portugal, Brazil and the Algarves from 1816 to 1825. Although the United Kingdom over which he ruled ceased to exist de facto beginning in 1822, he remained its monarch de jure between 1822 and 1825. After the recognition of Brazilian independence under the Treaty of Rio de Janeiro of 1825, he continued as King of Portugal and the Algarves until his death in 1826. Under the same treaty, he also became titular Emperor of Brazil for life, while his son, Pedro I of Brazil, was both de facto and de jure the monarch of the newly-independent country.
Born in Lisbon in 1767, the son of Maria I and Peter III of Portugal, he was originally an infante (prince, but not heir to the throne) of Portugal. He only became heir to the throne when his older brother José, Prince of Brazil, died of smallpox in 1788 at the age of 27.
Before his accession to the Portuguese throne, John VI bore the titles Duke of Braganza and Duke of Beja, as well as Prince of Brazil. From 1799, he served as prince regent of Portugal (and later, from 1815, as prince regent of the United Kingdom of Portugal, Brazil and the Algarves), due to the mental illness of his mother, Queen Maria I. In 1816, he succeeded his mother as monarch of the Portuguese Empire, with no real change in his authority, since he already possessed absolute powers as regent.
One of the last representatives of absolute monarchy in Europe, he lived during a turbulent period; his reign never saw a lasting peace. Throughout his period of rule, major powers, such as Spain, France and Great Britain, continually intervened in Portuguese affairs. Forced to flee to South America across the Atlantic Ocean into Brazil when troops of the Emperor Napoleon I invaded Portugal, he found himself faced there with liberal revolts; he was compelled to return to Europe amid new conflicts. His marriage was no less conflictual, as his wife, Carlota Joaquina of Spain, repeatedly conspired against her husband in favor of personal interests or those of her native Spain. He lost Brazil when his son Pedro declared independence, and his other son Miguel (later Miguel I of Portugal) led a rebellion that sought to depose him. According to recent scholarly research, his death may well have been caused by arsenic poisoning.