St. Mary's Cathedral, Roman Catholic cathedral in Calgary, Canada

St. Mary's Cathedral is a Roman Catholic church in Calgary with pointed arches, red brick walls, and sandstone trim following a T-shaped floor plan based on Saint Anthony's Cross. The interior holds Munich stained glass windows and a large statue of Mary holding the Christ Child.

St. Mary's began as a sandstone church built in 1889 near the Elbow River on land given by the Canadian Pacific Railway, in the Mission District where Father Albert Lacombe had settled in 1884. The land became the French-speaking village of Rouleauville, annexed by Calgary in 1907. When Pope Pius X created the Diocese of Calgary on 30 November 1912, the church became its cathedral. The sandstone building was demolished from 21 July 1955; the cornerstone of the new cathedral was laid on 30 October 1955, construction finished in February 1957, and Bishop Francis P. Carroll consecrated it on 11 December 1957.

The parish began as Notre-Dame-de-la-Paix, founded by Father Albert Lacombe, and the surrounding French-speaking village of Rouleauville was annexed by Calgary in 1907. The pulpit, carved in oak by the Globe Furniture Company of Waterloo, Ontario, shows Christ with the prophets Isaiah, Jeremiah, Ezekiel and Daniel. The 4.9-metre stone statue of the Virgin and Child above the main entrance was carved by Calgary sculptor Luke Lindoe.

The cathedral stands at 219 18 Avenue SW in the Mission district, a short walk from the Elbow River and the 17 Avenue SW bus corridor. The main entrance faces 18 Avenue, under the stone statue of the Virgin and Child. It is an active parish, so visits are best timed outside Mass; weekday daytime hours are the least busy.

Four bronze bells cast by a French foundry in 1904 were moved from the original church to the current building and still ring there today. These bells are an audible remnant from the earlier structure that stood over a century ago.