Field Marshal William Gustavus Nicholson, 1st Baron Nicholson, was a British Army officer who served in the Second Anglo-Afghan War, the Mahdist War, the Third Anglo-Burmese War, the Second Boer War and the First World War. He became Chief of the Imperial General Staff and was closely involved in the reorganisation of the British Army in the early years of the 20th century.

The Chief of the General Staff (CGS) has been the title of the professional head of the British Army since 1964. The CGS is a member of both the Chiefs of Staff Committee and the Army Board; he is also the Chair of the Executive Committee of the Army Board. Prior to 1964, the title was Chief of the Imperial General Staff (CIGS). Since 1959, the post has been immediately subordinate to the Chief of the Defence Staff, the post held by the professional head of the British Armed Forces.