Duncan William Ferguson Lamont (17 June 1918 - 19 December 1978) was a British actor. Born in Lisbon, Portugal, but brought up in Scotland, he had a long and successful career in film and television, appearing in a variety of high-profile productions.

On film, the best-known of the many productions he appeared in were The 39 Steps (1959, as Kennedy), Ben-Hur (1959, uncredited but playing Marius), Mutiny on the Bounty (1962, as John Williams), Arabesque (1966) and Battle of Britain (1969, as Flight Sergeant Arthur). Lamont is particularly memorable in his role as the wry, urbane Viceroy in Jean Renoir's The Golden Coach.

On television, he was a semi-regular in the series The Texan from 1958 to 1960, and appeared in guest roles in a range of popular British programmes from the 1950s to the 1970s, including The Adventures of Robin Hood, Dixon of Dock Green, Danger Man, The Avengers, Randall and Hopkirk (Deceased), The Persuaders!, and Doctor Who (the story Death to the Daleks).

In 1953, he appeared in the major role of astronaut Victor Carroon in the ground-breaking science-fiction serial The Quatermass Experiment, and fourteen years later returned to the series when he played the role of Sladden in the Hammer Films version of the third serial, Quatermass and the Pit.

He died in 1978 in Tunbridge Wells, Kent, of a heart attack at the age of sixty. He was working at the time on "Hostage", an episode of the BBC science-fiction series Blake's 7. Although he had completed location work for the episode, he died before the studio scenes had been shot, necessitating a re-mount of the location material in which he appeared and his replacement by the actor John Abineri.

He was married to the Irish actress Patricia Driscoll.

He should not be confused with Duncan Lamont, the composer for The Adventures of Spot and King Rollo.