Alistair Sim (October 9, 1900–August 19, 1976) was a Scottish actor.

Born in Edinburgh, Scotland, Sim was an elocution lecturer at New College, Edinburgh University from 1925 until 1930, and was rector from 1948 until 1951.

He made his first acting appearances in theatre during the 1930s, and his film debut in The Case of Gabriel Perry (1935). He spent the remainder of the decade playing supporting roles in films, and was often credited as "stealing the scene" from the leading actors. By the 1940s he had progressed to leading roles, and in 1950 he was voted the most popular film actor in Britain in a national cinema poll.

His films include Green for Danger (1946), Waterloo Road (1947), Alfred Hitchcock's Stage Fright (1950), Folly to be Wise (1953), The Belles of St. Trinian's (1954) and An Inspector Calls (also 1954) but arguably his most widely admired role was as the title character in Scrooge (1950). His most frequently played role was as Captain Hook in six different productions of Peter Pan between 1941 and 1968.

Sim was made CBE. He died in London, England from cancer.