St. Mary's of the Barrens Church is a Roman Catholic Church and former Seminary in Perryville, Missouri. St. Mary's is the historic seat of the American Vincentians and since its establishment in 1818 has served as an educational institution, a Vincentian house of formation, and a Vincentian community residence. The complex of eight contributing buildings, one contributing site, and two contributing structures was listed on the National Register of Historic Places in 1995 as St. Mary's of the Barrens Historic District. St. Mary's is the home of the National Shrine of Our Lady of the Miraculous Medal.