Infanta Mafalda of Portugal (c. 1195 – Rio Tinto, Gondomar, May 1, 1256; Portuguese pronunciation: [mɐˈfaɫdɐ]) was a Portuguese infanta (princess), later Queen consort of Castile for a brief period. She was the second youngest daughter of King Sancho I of Portugal and Dulce of Aragon. Married briefly to the ten-year-old Henry I of Castile, she held for a time the title Queen of Castile. Upon the dissolution of the marriage, she retired to religious life.