Group Captain W. G. G. Duncan Smith (May 28, 1914–December 11, 1996) was a World War II air ace. "Smithy" was responsible for 19 confirmed kills in aerial combat. He was awarded the Distinguished Service Order and Bar and the Distinguished Flying Cross and two Bars in recognition of his bravery.

He was the author of Spitfire into Battle, an account of aerial combat in the Spitfire aircraft.

In 1946, he married Pamela, a ballerina. Pamela's maternal grandmother was Ellen Oshey, a Japanese woman whose father was a Japanese artist. Their son Iain Duncan Smith is now a British politician, and was leader of the Conservative Party from September 2001 to November 2003.