- (1342-137?) Daughter of Pedro I of Portugal and Constanza Manuel.
- Married to Fernando de Aragon Marquis of Tortosa (1354), When her husband died she continued to live in Aragon.
- Later in life (c. 1370) had a close relationship with the Genoese Badasal or Baldassare Spínola, sold all her estate in Aragon and left to live with him in Genoa. Once her estate was spent, he abandoned her and she finished her days living with very reduced means. [Fernando, ch. 54: 38-44]
- Participates in the negotiations between King Pedro of Portugal and Pero IV of Aragon with a view to waging war on Enrique II of Castile and sealing a Luso-Aragonese alliance with the Marriage of Leonor, Princess of Aragon, to the Portuguese king. Accoding to Fernão Lopes, her advice had much impact in these negotiations. [Fernando, ch. 52: 8-9]
- In 1371, Princess Maria had a chest of weapons to send to her brother, Fernando of Portugal, but the King of Aragon confiscated it from her on the same occasion he confiscated King Fernando's treasure kept in Aragon, as part of the negotiations mentined above. The reason for that was King Fernandos unexpected agreement to a perpetual alliance with Enrique II of Castile, enemy of Aragon. [Fernando, 54: 24-28]