Infanta Maria, Marchioness of Tortosa
Maria of Portugal (6 April 1342, in Évora, Kingdom of Portugal – after 1375, in Aveiro, Kingdom of Portugal Portuguese pronunciation: [mɐˈɾiɐ]) was a Portuguese infanta (princess), first daughter of King Peter I of Portugal and his Queen consort Constanza Manuel.

Maria was born in Évora on 6 April 1342. In 1354, when she was only twelve years old, she married Fernando of Aragon, marquis of Tortosa, a marriage arranged by her grandfather, King Alfonso IV, to strengthen the alliance between the Kingdom of Portugal and the Crown of Aragon. Fernando was the son of King Alfonso IV and of his second wife, Eleanor of Castile.

Fernando was murdered by his half-brother Peter IV of Aragon in 1363. Maria then returned to Portugal where she died in the city of Aveiro after 1375. She is buried in Monastery of Santa Clara-a-Velha in Coimbra.