St. Mary's Church, Rostock, in German Marienkirche, is the biggest of three town churches found in the Hanseatic city of Rostock, in northern Germany. The other two are St. Peter's (Petrikirche) and St. Nicholas (Nikolaikirche). A fourth, St. James' (Jakobikirche), was heavily damaged during the Second World War and subsequently demolished. St. Mary's was designated in 1265 as the main parish church. Since the Protestant Reformation in 1531, it houses a congregation of the Evangelical Lutheran State Church of Mecklenburg.

Rostock officially the Hanseatic and University City of Rostock, is the largest city in the German state of Mecklenburg-Vorpommern and lies in the Mecklenburgian part of the state, close to the border with Pomerania. With around 210,000 inhabitants, it is the third-largest city on the German Baltic coast after Kiel and Lübeck, the eighth-largest city in the area of former East Germany, as well as the 39th-largest city of Germany. Rostock was the largest coastal and most important port city in East Germany.