Infanta Isabel Maria of Braganza (Portuguese pronunciation: [izɐˈbɛl mɐˈɾiɐ]; Queluz, 4 July 1801 – Benfica, then Belém, 22 April 1876) was a Portuguese infanta (princess) and fourth daughter of King John VI of Portugal and his wife Carlota Joaquina of Spain.

[1] She acted as regent for her brother Pedro IV and for her niece Maria II in 1826-1828.

Because Prince Pedro, who was heir to the throne, was already Emperor in Brazil, his brother Prince Miguel was exiled in Vienna, their mother Queen Carlota Joaquina was exiled in Queluz and Isabel's older sisters (Maria Teresa and Maria Francisca of Assisi) had married to Spanish infantes (princes), Isabel Maria was chosen to be Regent of the Kingdom until Pedro I of Brazil returned to claim the Portuguese throne as Pedro IV of Portugal.

Pedro and Maria remained in Brazil and Isabel Maria continued as regent until 1828, when a civil war started between absolutists, supporting Miguel, and liberals, supporting Maria II (called the Liberal War) that would end with a liberal victory and defeat and consequent exile of Miguel.

She died unmarried in Benfica (at the time not a neighbourhood of Lisbon but a near town in Belém municipality) on 22 April 1876.