Dom John VI (Portuguese: João VI;13 May 1767 – 10 March 1826), nicknamed "the Clement", was King of the United Kingdom of Portugal, Brazil and the Algarves from 1816 to 1822, and, although de facto the United Kingdom over which he ruled ceased to exist, he remained so de jure from 1822 to 1825; after the recognition of Brazilian independence under the 1825 Treaty of Rio de Janeiro, he continued as King of Portugal and the Algarves until his death in 1826. Under the said Treaty he also became Titular Emperor of Brazil for life, while his son, Emperor Pedro I, was both de facto and de jure the monarch of the newly independent country.

Born in Lisbon in 1767, the son of Peter III of Portugal, and Queen Maria I, he was originally an infante (prince not heir to the throne) of Portugal, and only became heir to the throne when his older brother, José, Prince of Brazil, died in 1788, of smallpox, at the age of 27.

Before his accession to the Portuguese throne, John VI bore the titles of Duke of Braganza and Duke of Beja, as well as the title of Prince of Brazil. He served, from 1799, 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, the Queen. Eventually, he succeeded his mother as monarch of the Portuguese Empire, with no real change in his authority, since, as Regent, he already possessed absolute powers.