The Archdiocese of Nueva Segovia is an archdiocese of the Catholic Church in the Philippines. It covers the province of Ilocos Sur, on the island of Luzon. The see of the archdiocese is the city of Vigan.

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.