Maria of Castile (1401-1458) was a daughter of Henry III of Castile and Catherine of Lancaster.
Her paternal grandparents were John I of Castile and his first wife Eleanor of Aragon. Her maternal grandparents were John of Gaunt, 1st Duke of Lancaster and his second wife Constance of Castile (1354-1394). Maria was also an older sister of John II of Castile.
Maria was betrothed to Alfonso V of Aragon in Valladolid in 1408; the marriage was celebrated in Valencia during 1415. Maria had delicate health, and was said to be unattractive. During Alfonso's wars in Italy, she acted as a regent in Aragon. Alfonso and Maria failed to produce children. She was buried in the convent of the Trinidad in Valencia.