Lieutenant-General Sir Willoughby Garnons Gwatkin, KCMG, CB (11 August 1859 – 2 February 1925) was a British Army officer who served as Chief of the General Staff of the Canadian Militia during the First World War.

The son of a barrister, Gwatkin was born in Twickenham, Middlesex, and was educated at Shrewsbury School, then at King's College, Cambridge. He later went to the Royal Military College, Sandhurst.^[1] He was commissioned into the Manchester Regiment as a lieutenant on 10 May 1882, in the same class as Herbert Lawrence, a future full general,^[2] and promoted to captain on 17 January 1890.^[3] He served as staff captain at headquarters when in January 1900 he was appointed a deputy assistant adjutant-general,^[4] followed by promotion to major on 7 April 1900. During the next year he returned as staff captain, until in October 1902 when he was appointed deputy assistant quartermaster-general.^[5] In 1905 he was posted to Canada as a staff officer and in 1907 he returned to Britain to attend Staff College and was promoted colonel while serving on half-pay.^[6]

In July 1913 he was appointed Chief Staff Officer, Canada, the first to be appointed by the Dominion Government instead of by the British War Office. In 1916 he was given the temporary rank of major-general. He retired from the Army in 1920 and was allowed to retain the honorary rank of major-general. He then served as Inspector-General of the Canadian Air Force until 1922 with the rank of air vice-marshal. In this role he provided advice and guidance to Air Commodore Arthur Tylee, Air Officer Commanding the Canadian Air Force. In 1922 Gwatkin was promoted honorary lieutenant-general in the Canadian Militia Reserve of Officers.

Gwatkin was appointed Companion of the Order of the Bath (CB) in 1916, Companion of the Order of St Michael and St George (CMG) in 1918, and Knight Commander of the Order of St Michael and St George (KCMG) in January 1920.^[7] In July 1924 he was appointed honorary colonel of the Manchester Regiment, dying six months later at the age of 65.

• Obituary, The Times, 4 February 1925
• Appreciation, Montreal Gazette, 25 March 1922

• Morton, Desmond (2005). "Gwatkin, Sir Willoughby Garnons". In Cook, Ramsay; Bélanger, Réal (eds.). Dictionary of Canadian Biography. Vol. XV (1921–1930) (online ed.). University of Toronto Press.
• McAndrew, William J. (14 December 2013). "Sir Willoughby Garnons Gwatkin". The Canadian Encyclopedia (online ed.). Historica Canada.