The Great Saint Martin Church (German: Groß Sankt Martin, mostly Groß St. Martin) is a Romanesque Catholic church in Cologne, Germany. Its foundations (circa 960 AD) rest on remnants of a Roman chapel, built on what was then an island in the Rhine. The church was later transformed into a Benedictine monastery. The current buildings, including a soaring crossing tower that is a landmark of Cologne's Old Town, were erected between 1150-1250. The architecture of its eastern end forms a triconch or trefoil plan, consisting of three apses around the crossing, similar to that at St. Maria im Kapitol. The church was badly damaged in World War II, with restoration work completed in 1985.
As of 2009 Great Saint Martin is being used by a branch of the Monastic Fraternities of Jerusalem and is open for visits again.