Old St. Mary's Church is a Roman Catholic church in Cincinnati's historic Over-The-Rhine neighborhood. It is the oldest continually-used house of worship in Cincinnati. Old St. Mary's is the oldest church in Cincinnati, and since 2017, home to The Cincinnati Oratory, a society of priests and brothers of The Congregation of the Oratory of St. Philip Neri. The ch…Old St. Mary's Church is a Roman Catholic church in Cincinnati's historic Over-The-Rhine neighborhood. It is the oldest continually-used house of worship in Cincinnati. Old St. Mary's is the oldest church in Cincinnati, and since 2017, home to The Cincinnati Oratory, a society of priests and brothers of The Congregation of the Oratory of St. Philip Neri. The church was organized in 1840 by German immigrants, at a time of dramatic growth in the city's population.