The Saint Mary of Loreto Church of Achao (Iglesia Santa María de Loreto de Achao) is a Catholic Temple located in front of the Central Square of the city of Achao, capital of the municipality of Quinchao. Its access overlooks the sea, finding itself two blocks from the coast.

Built in wood with three naves, it was constructed by the Jesuit around 1730 and rebuilt in 1784 after a fire. It is considered one of the oldest churches in Chile. The church is 46 meters long, 14 meters wide, and its tower measures 22 meters. On the outside it is covered with larch shingles. Its skeleton was crafted mainly with mañio, cypress, and many of its joints are made with wooden pegs. In its interior, which is still a stage for mass and other activities, the architecture is inspired in baroque designs made in wood, such as the altarpiece located behind the altar, and its pulpit thoroughly decorated with wooden patterns. The central vault is divided into five channels with caps in carved patterns. The rustic wooden boards of its floor were cut using an axe. The columns are Solomonic and hold plant ornaments proper of baroque style.

It was declared National Monument in July 1951, and World Heritage by UNESCO in the year 2000. Its main festivity is celebrated on December 10, honoring Saint Mary of Loreto, patron of the church.