A regent is “a person appointed to administer a state because the monarch is a minor, is absent or is incapacitated.”
Luisa de Guzmán was born on 31 October 1613 as the daughter of Juan Manuel Pérez de Guzmán, 8th Duke of Medina Sidonia and Juana Lorenza Gomez de Sandoval y la Cerda.
On 12 January 1633, she married John, 8th Duke of Braganza. The couple would go on to have seven children, including two future Kings of Portugal and a Queen of England. She was known to be ambitious and ruthless. She influenced her husband to accept the Portuguese thrones during the Portuguese revolution against the Habsburg rule in Spain in 1640, where she supposedly spoke the famous words:
Rather Queen for a day than Duchess all my life.
On 1 December 1640, John was proclaimed King of Portugal, as he claimed legitimate descent from his grandmother, Catherine, Duchess of Braganza (a granddaughter of King Manuel I of Portugal).
Luisa was widowed in 1656 while her son, now King Afonso VI, was just 13 years old. She was named as Regent of the Kingdom for the duration of his majority. However, she continued to act as regent even after this period ended because her son was mentally unstable.
She was politically shrewd, and she controlled the government, while her son was unable to. She hoped (as would happen) that her youngest son would eventually succeed as King. She succeeded in creating a new political alliance with England when her daughter Catherine married King Charles II of England. 1