Maria Stein is an unincorporated community and census-designated place in Marion Township, Mercer County, Ohio, United States. As of the 2020 census, the population was 1,067. The community and the Maria Stein Convent lie at the center of the area known as the Land of the Cross-Tipped Churches, where a missionary priest, Father Francis de Sales Brunner, established a number of parishes for German Catholics.