María del Pilar Sinués y Marco (Zaragoza, December 19, 1835 - Madrid, April 20, 1893) was a Spanish writer, popularly known for her serialized novels and short stories. She was one of the most prolific and widely read authors of her time. Her work is characterized by dealing with romantic, costumbrista, and moralizing themes, with a style accessible to the general public. She published over 100 novels, in addition to articles and poems. She was the first woman to join the Royal Spanish Academy in 1876, although as a "corresponding academician" and not a full member, which limited her participation. Her influence was significant in 19th-century popular literature in Spain.