Maria de las Mercedes

(1880 –1904) was the eldest child of King Alfonso XII of Spain and his second wife, Maria Christina of Austria. She was Princess of Asturias, the heir presumptive to the Crown of Spain, for all 24 years of her life.
Had her younger sibling, unborn at the death of Alfonso XII, been a daughter, Mercedes would have been Queen of Spain. The sibling proved to be a boy, Alfonso XIII.