The Iglesia San Blas de Illescas () is a Catholic parish church located on the center plaza of Coamo, Puerto Rico. Construction on the church began in 1661; it has since been judged "one of the most important works of religious architecture in Puerto Rico".
The church is separated from the open plaza below by a series of ceremonial steps and a delicate cast iron balustrade. The delicately curved Baroque facade reflects a major reconstruction completed in 1784. A two-level bell-gable with open arches and bells is prominently featured in the facade. The parish of San Blas of Coamo is one of the oldest on the island.