St. Stanislaus Kostka Church is an independent Catholic church located in the city of St. Louis, Missouri, United States. Formerly a parish belonging to the Catholic Church, it was established in 1880 to serve the Polish community in the Archdiocese of St. Louis. It is considered to be the best example of the opulent Polish Cathedral style of architecture west of the Mississippi River. The parish continues to be maintained and managed by its parishioners as a not-for-profit corporation, calling itself "Catholic", but unaffiliated with the Roman Catholic Church.