St. Martin's (German: St. Martini) is a Lutheran church in Groß Ellershausen, Göttingen, Lower Saxony, Germany. It is significant as possibly retaining the oldest existing structure, its tower, in southern Lower Saxony. While the details of the origin of the church building have been lost in the mist of history, architectural analysis indicates that the Romanesque church tower was most likely built in the tenth or eleventh century. The remains of a hearth on the second floor have led to the conclusion that the tower was originally a Wohnturm (a residential tower) of a titled family, probably the Herren von Ellershausen, which lived there at the time. The church's ship is much younger, probably having been built or re-built during the Barocque era.