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.

The German city of Hildesheim, c. 30 kilometres south of Hanover, was the target of eight Allied air raids in 1944 and 1945 and suffered considerable bomb damage.