St. Mary's Church in Gardelegen is an outstanding example of brick Gothic architecture and serves as the town's main place of worship. The church's origins date back to around 1200, when a smaller, Romanesque church was built on this site. In the 13th century, it was expanded into a five-aisled hall church with a square west tower. After a devastating fire in 1306, the long choir was rebuilt with a five-eighths end.
At the end of the 15th century, the main nave was raised and vaulted. A dramatic incident occurred on May 15, 1658, when a large section of the church tower collapsed during a service, killing 22 people. The reconstruction of the tower dragged on until 1691.
The church houses several important furnishings, including a four-winged, fully gilded altarpiece from around 1430 depicting the Coronation of the Virgin Mary. Additional altars from the late 15th century and a double figure of St. Anne the Self-Proclaimed enhance the furnishings. The organ by Christoph Treutmann from 1723, restored in 2013, has 25 stops and is one of the church's outstanding musical treasures. St. Mary's Church continues to be used for services, sacraments, and concerts. Extensive renovation work was carried out between June 2022 and September 2023 to improve and preserve the church's furnishings.