Doña Carlota Joaquina Teresa Cayetana of Spain (25 April 1775 – 7 January 1830) was Queen of Portugal and Brazil as the wife of King Dom John VI.

After the escape of the Portuguese court to Brazil, she began conspiring against her husband, claiming that he had no mental capacity to govern Portugal and its possessions, thus wanting to establish a regency.

She received a rigid and deeply Catholic education, with bases in the fields of study of religion, geography, painting, and riding (Carlota's favorite sport).

King Charles III, a man of reserved behavior, devoted more time to his family than to the animations of the courtesan life, where his daughter-in-law Maria Luisa took an active part.

Carlota's apprenticeship would be tested when she underwent a series of public examinations in front of the Spanish court and Portuguese ambassadors sent on behalf of Queen Maria I of Portugal to evaluate the qualities of the princess destined to marry her second son.

In October 1785, the Gazeta of Lisbon published an account of the tests: "Everything has satisfied so completely that one can not express the admiration which such a vast instruction ought to cause at such a tender age: but...the decided talent with which God has endowed this most serene Lady, her prodigious memory, understanding and that everything is possible, especially with the awakening and capacity with which the above-mentioned master promotes such useful and glorious applications.

"Having proven the talent of the bride, there was therefore no impediment to the union with the Portuguese prince, so on 8 May 1785 was celebrated the proxy marriage; three days later, on 11 May, the 10-year-old Carlota Joaquina and her retinue left Spain for Lisbon.

As a part of the infanta cortege were Father Felipe Scio, famous Spanish theologian and scholar, Emília O'Dempsy, as lady-in-waiting, and Anna Miquelina, personal maid of Carlota Joaquina.

While in other parts of the Europe they represented the mark of a new society based on the Age of Enlightenment principles, in Portugal the Catholic Church still imposed norms prohibiting all types of amusement.

Quite traditional in relation to female behavior, Portuguese men disapproved of the ease with which Carlota Joaquina transited in public space, her performance in the political field and her distemper in the family routine.

Since most Portuguese women were deprived of social life, Carlota Joaquina's offending behavior allowed some malicious rumors about her in the court.

During her time in Lisbon, Madame Junot had ridiculed Carlota Joaquina both for her manner of acting and for her dressing, and she had vilified her as an extremely ugly woman.

The Portuguese-Brazilian forces, however, only managed to temporarily annex the eastern banks of the Rio de la Plata as Cisplatina, which were kept in the Empire of Brazil after 1822 and seceded in 1828 as the Republic of Uruguay.

John VI refused to accept this until he was persuaded by the British to do so, signing in August 1825 the Treaty of Rio de Janeiro by which he and Carlota Joaquina were granted the honorific title of Emperors of Brasil.

Abandoned by all her family and betrayed by her friends and allies, Queen Carlota Joaquina died alone at the Queluz Royal Palace, outside of Sintra.

After her death, Carlota Joaquina (mainly in Brazil) became part of popular culture and an important historical figure, being the subject of several books, films and other media.