Maria de las Mercedes of Orleans (1860 – 1878) was Queen Consort of Spain, the first wife of Alfonso XII. She was born in Madrid, Spain, the daughter of Antoine of Orléans, Duke of Montpensier and of Infanta Luisa Fernanda of Spain.
When Queen Isabella II was deposed in 1868, Mercedes' family left Spain for exile. It was reportedly during that banishment, in 1872, that she met her first cousin, Alfonso, Prince of Asturias, also living in exile.
Upon restoration, King Alphonso married Maria de la Mercedes at the church of Atocha, in Madrid on 23 January 1878, following a huge ball in December 1877. Allegedly the king's choice dashed the hopes of his still-exiled mother, Queen Isabella, for Alfonso's marriage to the Blanca de Borbón, daughter of his Carlist rival, Carlos, Duke of Madrid.
However, shortly after their honeymoon, it became evident that the bride had tuberculosis. The marriage would last only six months, during which she had a miscarriage. Queen Mercedes succumbed to the illness in Madrid two days after her 18th birthday, on 26 June 1878, having been unconscious for several days.
Her corpse was arrayed in the black and white vestments of a nun and she was buried at the Escorial, although not in the royal crypt where, by tradition, only queens who had given birth to a royal heir were interred.
Queen Mercedes co-initiated the building of the Cathedral of la Almudena in Madrid, opposite the royal palace, construction beginning in 1883. In May 2004 Felipe, Prince of Asturias was wed there to Letizia Ortiz. Queen Mercedes' remains were re-interred there on 8 November 2000, in accordance with the wishes of her widower.