Henry Duncan Graham Crerar, (28 April 1888 – 1 April 1965) was a senior officer of the Canadian Army who became the country's senior field commander in the Second World War as commander of the First Canadian Army in the campaign in North West Europe in 1944–1945, having rapidly risen in rank from brigadier in 1939 to full general in 1944.
A graduate of the Royal Military College of Canada in Kingston, Ontario, Crerar was commissioned as a lieutenant in the Non-Permanent Active Militia in 1909, serving with the 4th Battery, Canadian Field Artillery, which was based in Hamilton, Ontario. He rose to the rank of lieutenant-colonel in the artillery. He saw action in the First World War, for which he was mentioned in despatches and made a companion of the Distinguished Service Order. Electing to remain in the army as a professional soldier after the war, he attended the Staff College, Camberley, from 1923 to 1924, and the Imperial Defence College in 1934.