The Diocese of Cleveland is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in northeastern Ohio in the United States. As of September 2020, the bishop is Edward Malesic. The Cathedral of St. John the Evangelist, located in Cleveland, is the mother church of the diocese.

The Cathedral of St. John the Evangelist is a historic Roman Catholic church building located at 1007 Superior Avenue in Cleveland, Ohio, in the United States. Completed and consecrated in 1852, it is the cathedral of the Roman Catholic Diocese of Cleveland. Numerous renovations have enlarged and changed some aspects of the cathedral, but it remains essentially the same since its construction.