Mariana Victoria of Portugal (or of Braganza; Portuguese: Mariana Vitória; pronounced [mɐɾiˈɐnɐ]; full name: Mariana Vitória Josefa Francisca Xavier de Paula Antonieta Joana Domingas Gabriela de Bragança; Portuguese: [mɐˈɾiɐ ˈɐnɐ viˈtɔɾiɐ ʒuˈzɛfɐ]; 15 December 1768 – 2 November 1788) was a Portuguese Infanta (princess), the eldest daughter of Queen Maria I of Portugal and her king-consort, Infante Pedro of Portugal.

While there, she helped to bring about the marriage of Mariana Victoria and the Spanish king's younger son, Infante Gabriel, her mother's first cousin.

Upon her early death, her son Pedro was recognized by his Portuguese grandmother as an infante of Portugal, in addition to his Spanish infantizado from their paternal side.

She and her husband were the founders of the House of Bourbon-Braganza which subsequently joined the Spanish nobility as dukes of Marchena, Durcal, Hernani and Ansola.

Mariana Victoria was buried at the Royal Monastery of El Escorial with her husband and her two young children.