Mary, Queen of the World Cathedral or in full Mary, Queen of the World and St. James the Great Cathedral is a minor basilica in Montreal, Quebec, Canada, and the seat of the Roman Catholic Archdiocese of Montreal. It is the third largest church in Quebec after Saint Joseph's Oratory and the Basilica of Sainte-Anne-de-Beaupré east of Quebec City. The building is 101 m (333 ft) in length, 46 m (150 ft) in width, and a maximum height of 77 m (252 ft) at the cupola, the diameter of which is 23 m (75 ft).

The Roman Catholic Archdiocese of Montréal is a Latin Church ecclesiastical territory or archdiocese of the Catholic Church in Canada. A metropolitan see, its archepiscopal see is the Montreal, Quebec. It includes Montreal and surrounding areas within Quebec.