Hildesheim Cathedral, officially the Cathedral of the Assumption of Mary or simply St. Mary's Cathedral, is a medieval Roman Catholic cathedral in the city centre of Hildesheim in Lower Saxony, Germany, that serves as the seat of the Diocese of Hildesheim. The cathedral has been on the UNESCO World Cultural Heritage list since 1985, together with the nearby St. Michael's Church because of its unique art and outstanding Romanesque architecture.

Hildesheim is a city in Lower Saxony, in north-central Germany with 101,693 inhabitants. It is in the district of Hildesheim, about 30 km (19 mi) southeast of Hanover on the banks of the Innerste River, a small tributary of the Leine River.