Ilocos Sur, officially the Province of Ilocos Sur, is a province in the Philippines located in the Ilocos Region in Luzon. Located on the mouth of the Mestizo River is the capital of Vigan. Ilocos Sur is bordered by Ilocos Norte and Abra to the north, Mountain Province to the east, La Union and Benguet to the south and the South China Sea to the west.

The Archdiocesan Shrine of Our Lady of the Assumption, commonly known as the Santa Maria Church and Santa Maria Pro-cathedral, is a Roman Catholic shrine in Santa Maria, Ilocos Sur, Philippines. The church was designated as a UNESCO World Heritage Site on December 11, 1993, as part of the Baroque Churches of the Philippines, a collection of four Baroque Spanish-era churches. It is currently the pro-cathedral of the Archdiocese of Nueva Segovia while the Vigan Cathedral is undergoing repairs.