St. Mary Roman Catholic Church, Detroit

Saint Mary Roman Catholic Church, formally the Church of the Immaculate Conception of the Blessed Virgin Mary is the third oldest parish in Detroit. It is located at 646 Monroe Street in heart of Greektown Historic District within Detroit's downtown area. It is often called Old Saint Mary's Church to avoid confusion with other Saint Mary's parishes in the Redford neighborhood of Detroit or nearby Royal Oak, Monroe, or Wayne.

The complex originally consisted of the church, rectory, constructed in 1876, school, constructed in 1868, and convent, completed in 1922. The convent was demolished in the early 2000s and replaced with a community center designed to resemble the 1841 church building. Saint Mary Parish has been staffed by the Spiritans or Holy Ghost Fathers since 1893. It was previously administered by the Franciscan Fathers (1872-1893) and the Redemptorist Fathers (1847-1872).