San Agustin Church, commonly referred to as Paoay Church, is one of the most iconic Roman Catholic church structures in the Philippines.

Among the major attractions in the Ilocos region, this early 18th-century church is famous for its distinctive Baroque-style architecture, featuring massive coral stone buttresses on the sides and back of the building, spanning 110 metres (360 ft) long and 40 metres (130 ft) wide.

The original parish was founded by Augustinian missionaries in 1593, and the cornerstone of the present structure was initially laid out in 1704, under the Augustinian friar Antonio Estavillo.

Damaged by the earthquake of 1706, the church was kept in repair and used before completion by the people under the joint auspices of the church and town officials.

The convent was added in 1707, and the impressive edifice was completed in 1710. The bell tower was added later in 1793.

The tower was used as an observation post by Katipuneros during the revolution, and by guerrilleros during the Japanese occupation.

Declared a National Cultural Treasure by the Philippine government in 1973, the church was designated a UNESCO World Heritage Site under the collective group of Baroque Churches of the Philippines in 1993.