Old St. Mary's Church, Cincinnati

Old Saint 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 Saint 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 Saint Philip Neri. The church was organized in 1840 by German immigrants, at a time of dramatic growth in the city's population.

Designed in the Greek Revival style by Franz Ignatz Erd, it is the second-oldest German-Catholic parish in the city and the oldest standing church in Cincinnati. The church is 142 feet long, 66 feet wide and with a steeple 170 feet tall. When built, it was the largest church in the Ohio Valley. The original church was dedicated on July 3, 1842.

The three buildings of the Old Saint Mary's parish complex were listed together on the National Register of Historic Places in 1976.