The 39 Steps is a 1935 British spy thriller film directed by Alfred Hitchcock, starring Robert Donat and Madeleine Carroll. It is loosely based on the 1915 novel The Thirty-Nine Steps by John Buchan. It concerns a Canadian civilian in London, Richard Hannay, who becomes caught up in preventing an organisation of spies called "The 39 Steps" from stealing British military secrets. Mistakenly accused of the murder of a counter-espionage agent, Hannay goes on the run to Scotland and becomes tangled up with an attractive woman, Pamela, while hoping to stop the spy ring and clear his name.

Since its initial release, the film has been widely acknowledged as a classic. Filmmaker and actor Orson Welles referred to it as a "masterpiece". Screenwriter Robert Towne remarked, "It's not much of an exaggeration to say that all contemporary escapist entertainment begins with The 39 Steps."