The 31st Battalion (Alberta), CEF, was an infantry battalion of the Canadian Expeditionary Force during the Great War. 

The battalion recruited in Alberta and was mobilized at Calgary. 

The battalion was raised at Calgary, and started recruitment in Alberta, on 7 November 1914.

On 17 May 1915, the battalion sailed for England on RMS Carpathia, with a complement of 36 officers and 1033 other ranks.

On 18 September 1915 it disembarked in France, where it fought with the 6th Infantry Brigade, 2nd Canadian Division in France and Flanders until the end of the war. 

After initial training in England, the battalion fought in Belgium and France, and was often at the forefront of the fighting at : 

• St. Eloi Craters

• the Ypres Salient, 

• Vimy Ridge (Thélus Village)

• Fresnoy, Somme

• Second Battle of Passchendaele 

• the Battle of Amiens (1918), the Battle of Arras (1917)

• Battle of Drocourt-Quéant Line 

• Valenciennes 

• Mons

• the occupation of the Rhineland

The battalion captured a Siberian pony from the Germans, which apparently had been captured from the Russians earlier in the war. 

The Canadians named this pony Heinie, and it became the 31st Battalion's mascot. 

After the war the 31st brought Heinie to Alberta, where it worked until at least the late 1920s for the Dominion Parks Branch near Banff, Alberta.

The bulk of the battalion returned to Canada on SS Cedric on 27 May 1919, and to Calgary on 1 June 1919, with the unit's disbandment occurring on 30 August 1920.

Through the course of the First World War, the 31st Battalion suffered losses of 941 dead, and an additional 2,312 non-fatal casualties. A total of 4,487 men served in the battalion.