Major-General Sir Sydney D'Aguilar Crookshank (3 June 1870 – 17 August 1941) was a British military engineer who served with the Royal Engineers in the British Army and the British Indian Army.
Most of his early career was spent in colonial service; he later served as a senior officer during the First World War.As a temporary Lieutenant-Colonel he was Commander, Royal Engineers (CRE), of 47th (1/2nd London) Division on the Western Front from 30 July 1915 to 27 November 1916.
On 21 May 1916 in the Vimy sector the Germans fired a mine and attacked the division's positions in overwhelming numbers.
The situation was so critical for a while that Crookshank brought his Sappers of 47th (2nd London) Divisional Engineers up to man the trenches as infantry.
He was awarded a Distinguished Service Order on 3 June 1916.
Later, as a Major-General he was appointed Director-General (Transportation) of the British Armies in France on 19 March 1918.After the war, Crookshank was appointed Honorary Colonel of 47th (2nd London) Divisional Engineers on 3 March 1923.