María Díaz de Padilla (c. 1334[a] –Seville, July 1361) was the mistress of King Peter of Castile, whom he posthumously recognised as his wife.

[2] María's family, members of the regional nobility,[3] originally came from the area of Padilla de Abajo, near Castrojeriz in the province of Burgos.

[c] King Peter met María in the summer of 1352 during an expedition to Asturias to battle his rebellious half-brother Henry.

[4] In the summer of 1353, under coercion from family and the main court favorite, Juan Alfonso de Alburquerque, Peter wed Blanche of Bourbon, the first cousin of King John II of France.

Peter abandoned Blanche within three days when he learned that she had an affair with his bastard brother Fadrique Alfonso en route to Spain, and that the dowry was not coming.