St. Augustine Tower or Church of St. Augustine is a ruined church complex located in Old Goa. The church was completed in 1602 and is part of the World Heritage Site, Churches and convents of Goa. The church was built on top of the Monte Santo (Holy Hill) between 1597 and 1602 by Augustinian friars who landed in Goa in 1587. The church was considered as one of the three great Augustinian churches in the Iberian world along with El Escorial and the Monastery of São Vicente de Fora.
In 1835, the church was abandoned after the Portuguese government of Goa began evicting many religious orders in Goa under its new repressive policies. The subsequent neglect caused the vault of the church to collapse in 1842. The body collapsed soon after and by 1871, the bell was moved from the tower to Our Lady of the Immaculate Conception Church in Panjim, where it remains to date. In 1931, the facade of the church and half the tower collapsed and by 1938, most of the other parts had also collapsed. Currently only half the tower remains, and it is one of the most visited tourist destinations in Goa. The church had four towers of which only one remains. The remaining tower is a four-storied structure built of laterite and 46 m in height. Excavations show that the complex had eight chapels, four altars and a convent.