Major General Sir James Howden MacBrien KCB CMG DSO CStJ (30 June 1878 – 5 March 1938) was a Canadian soldier and Chief of the General Staff, the head of the Canadian Militia (renamed the Canadian Army in 1940) from 1920 until 1927.

Educated in Port Perry (Port Perry High School),^[1] MacBrien initially joined the Canadian Militia with the 34th Ontario Regiment but then transferred to the North-West Mounted Police and, during the Second Boer War, to the South African Constabulary.^[1][2] Returning to Canada he was commissioned into the Royal Canadian Dragoons.^[1]

He also served in World War I as a general staff officer and then, from 1916, as commanding officer of 12th Infantry Brigade.^[2]

After the war he was appointed Chief of the General Staff.^[2]

He also served as the eighth Commissioner of the Royal Canadian Mounted Police, from August 1, 1931 to March 5, 1938.^[1] MacBrien died in Toronto.

In 1907 he married Nellie Louise Ross and in 1928 he married Emily Emely Hartridge.^[1]