Sir Walter Gordon Duncan (10 March 1885 – 27 August 1963) was a politician in the State of South Australia.

He was educated at St Peter's College, where he did not shine academically, but excelled at cricket.

He was elected to the South Australian Legislative Council for the Liberal Party by the Midland electorate in March 1918 and was re-elected in 1924, 1930, 1938, 1944, 1950 and 1956, finally retiring in 1962.

He was elected President of the South Australian Legislative Council in 1944 and held the position until 1962.

He married Bessie Graham Fotheringham on 20 October 1922; they lived at 56 Park Terrace (now Greenhill Road), Parkside.