The 31st Division was an infantry division of the British Army. It was raised in the Great War by volunteers from Kitchener's Army and formed in April 1915 as part of the K4 Army Group and taken over by the War Office on 10 August 1915. Comprising mainly infantry battalions from Yorkshire and Lancashire, the division was sent to Egypt in December 1915 before moving to France in March 1916 and spent the remainder of the First World War in action on the Western Front. The 31st Division was the quintessential New Army division, being made up entirely of Pals battalions.

The New Army, often referred to as Kitchener's Army or, disparagingly, as Kitchener's Mob, was an (initially) all-volunteer portion of the British Army formed in the United Kingdom from 1914 onwards following the outbreak of hostilities in the First World War in late July 1914. It originated on the recommendation of Herbert Kitchener, then the Secretary of State for War to obtain 500,000 volunteers for the Army. Kitchener's original intention was that these men would be formed into units that would be ready to be put into action in mid-1916, but circumstances dictated the use of these troops before then. The first use in a major action of Kitchener's Army units came at the Battle of Loos.