The Metropolitan Cathedral of the Most Holy Trinity, is a Roman Catholic Cathedral in Buenos Aires, the capital city of Argentina. It is located in the city center, overlooking Plaza de Mayo, on the corner of San Martín and Rivadavia streets, in the San Nicolás neighbourhood. It is the mother church of the Archdiocese of Buenos Aires and held the rank of Primatial church of Argentina from 1822 to 2024. The cathedral was declared National Historic Monument in 1942.