The Castle of the Teutonic Order in Malbork (Polish: zamek w Malborku; German: Ordensburg Marienburg) is the largest castle in the world by surface area. It was built in Marienburg, Prussia (now Malbork) by the Teutonic Knights, a German Roman Catholic religious order of crusaders, in a form of an Ordensburg fortress. The Order named it Marienburg (Mary's Castle).