Maria Stein is a census-designated place in central Marion Township, Mercer County, Ohio, United States. 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.

Marion Township is one of the fourteen townships of Mercer County, Ohio, United States. The 2020 census found 3,322 people in the township.