San Sebastian Church is a Roman Catholic church located in the Quiapo district of Manila, Philippines. It is considered as the only all-steel church in Asia, and also one of the few surviving examples of Gothic Revival architecture in the Philippines. The church was built by Spanish architect Genaro Palacios in the late 19th century, with the aim of creating a fire-resistant building due to the previous church's destruction by earthquakes and fires.

The church's facade features intricate steel filigree work, which was manufactured in Belgium and shipped to the Philippines. Its interiors, on the other hand, are characterized by a Gothic style, with stained glass windows, an elaborately designed altar, and towering spires. San Sebastian Church has been recognized as a National Historical Landmark by the Philippine government in 1973, and was also declared as a National Cultural Treasure in 2011.

San Sebastian Church is also known for its association with the Katipunan, a Philippine revolutionary society that played a key role in the country's fight for independence from Spanish colonial rule. In 1896, the society held a secret meeting inside the church, which was led by its founder, Andres Bonifacio.

Today, San Sebastian Church remains an important landmark in the Quiapo district and is a popular destination for both tourists and religious pilgrims. It also serves as a venue for cultural events and activities, such as concerts and exhibits.