St. Mary's Cathedral is a cathedral church located in Winnipeg, Manitoba. It is the episcopal see of the Roman Catholic Archdiocese of Winnipeg. Located at the corner of St. Mary Avenue and Hargrave Street in downtown Winnipeg, St. Mary's is one of two Roman Catholic cathedrals in the city of Winnipeg; the other, St. Boniface Cathedral, is located across the Red River in the formerly independent city of Saint Boniface. The Institute for stained glass in Canada has documented the stained glass at St. Mary's Cathedral.