María Mercedes Fontecilla y Fernández de Valdivieso (June 18, 1799 – May 5, 1853) was a First Lady of Chile.
Mercedes Fontecilla was born in Santiago, the daughter of Diego Antonio Fontecilla Palacios and of Rosa Fernández de Valdivieso y Portusagasti. She married José Miguel Carrera Verdugo on August 20, 1814, and together they had five children: Francisca Javiera, Roberta, Rosa, Josefa and José Miguel (who was born after the death of his father, and was in turn the father of Ignacio Carrera Pinto, hero of the War of the Pacific.) After the defeat of Rancagua, together with her husband, she emigrated to Argentina. Mercedes Fontecilla followed him during all his campaigns and was allowed to return to Chile only in 1821.
After the execution of General Carrera in 1823, she married Diego José Benavente Bustamante, with whom she another four children: Benjamín, Mercedes, Mariana and Carolina. She died in Santiago at the age of 54.