St. Mary's parish church first appeared in records in 1187. The current chancel and the southern side aisle were built in 1280 or thereabouts. Between 1412 and 1439, the triple-naved hall replaced the nave and the towers were erected.
St. Mary's Church, as the town, parish and people's church, was where the reformers Martin Luther and Johannes Bugenhagen preached their sermons. The service was held in German for the first time here and Communion distributed among the congregation for the first time 'in both kinds', i.e. with bread and wine.
In 1535, the church also witnessed the first ordinations of Protestant priests, which makes it the mother church of the Reformation.