The 3rd Canadian Division is a formation of the Canadian Army responsible for the command and mobilization of all army units in the provinces of Manitoba, Saskatchewan, Alberta and British Columbia, as well as all units extending westwards from the city of Thunder Bay.

The Canadian Corps was a World War I corps formed from the Canadian Expeditionary Force in September 1915 after the arrival of the 2nd Canadian Division in France. The corps was expanded by the addition of the 3rd Canadian Division in December 1915 and the 4th Canadian Division in August 1916. The organization of a 5th Canadian Division began in February 1917 but it was still not fully formed when it was broken up in February 1918 and its men used to reinforce the other four divisions.