María Díaz de Padilla (María de Padilla) (1334 – August 1361) was the mistress of Pedro I, King of Castile, whom she married in secret in 1353.
She was a Castilian noblewoman. Her father was Juan García de Padilla, 1st Lord of Villagera, her mother was his wife María Fernández de Henestrosa, a relative of Juan Fernández de Henestrosa, who mediated an apparent pardon to Fadrique Alfonso of Castile, a half-brother and rival of María de Padilla's lover Pedro I.
In the summer of 1353, under coercion from family and court nobles, Pedro denied the fact of his marriage to María to marry Blanca of Bourbon, but his relationship with María continued. María and Pedro I had at least four children: a daughter named Beatriz (born 1354), a daughter named Isabella (1355–1394), another daughter named Constance (1354–1394), and a son named Alfonso, crown-prince of Castile (1359 - October 19, 1362).
