John Grant "Jack" Duncan-Hughes MC (1 September 1882 – 13 August 1962) was an Australian politician. He was a member of the Australian House of Representatives for Boothby from 1922 to 1928, of the Australian Senate for South Australia from 1932 to 1938, and of the House of Representatives for Wakefield from 1940 to 1943. He represented the Nationalist Party (1922–28) and its successor the United Australia Party (1932–38, 1940–43).