Mainz Cathedral or St. Martin's Cathedral (German: Mainzer Dom, Martinsdom or, officially, Der Hohe Dom zu Mainz) is located near the historical center and pedestrianized market square of the city of Mainz, Germany. This 1000-year-old Roman Catholic cathedral is the site of the episcopal see of the Bishop of Mainz.
Mainz Cathedral is predominantly Romanesque in style, but later exterior additions over many centuries have resulted in the appearance of various architectural influences seen today. It comprises three naves and stands under the patronage of Saint Martin of Tours. The eastern quire is dedicated to Saint Stephen.