Joanna of Portugal OP was a Portuguese regent princess of the House of Aviz, daughter of King Afonso V of Portugal and his first wife, Queen Isabel of Coimbra. She served as regent during the absence of her father in 1471. In 1475 she became a cloistered nun of the Dominican Order. She is venerated in the Catholic Church with the title 'Blessed', is commemorated by a feast on May 12, and is commonly known in Portugal as Holy Princess Joan.
