The Man Who Knew Too Much is a 1934 British spy thriller film directed by Alfred Hitchcock for Gaumont British. Starring Leslie Banks and Peter Lorre, it was one of the most successful and critically acclaimed films of Hitchcock's British period.

Hitchcock remade the film in 1956, with James Stewart and Doris Day in leading roles. The two films are very similar in tone and plot, with significant modifications. In the book-length interview Hitchcock/Truffaut (1967), in response to filmmaker François Truffaut's assertion that aspects of the remake were by far superior, Hitchcock replied, "Let's say the first version is the work of a talented amateur and the second was made by a professional." However, some critics have concluded that Hitchcock's statement should not be taken at face value.

The 1934 film has nothing except the title in common with G. K. Chesterton's 1922 book of the same name. Hitchcock decided to use the title because he held the film rights for some of the stories in the book. The film started when Hitchcock and writer Charles Bennett tried to adapt a Bulldog Drummond story revolving around international conspiracies and the kidnapping of a baby; its original title was Bulldog Drummond's Baby. The deal for an adaptation fell through, and the frame of the plot was reused in the script for The Man Who Knew Too Much, the title itself taken from an unrelated G.K. Chesterton compilation.

The story is credited to Bennett and D. B. Wyndham Lewis. Bennett claimed that Lewis had been hired to write some dialogue that was never used and provided none of the story, though this account has been disputed.

It was Peter Lorre's second English-language film, following the multiple-language version of M (1931). But he was still unable to speak English, having only recently fled Nazi Germany, and learned his lines phonetically.

The shoot-out at the end of the film was based on the Sidney Street Siege, a real-life incident that took place in London's East End (where Hitchcock grew up) on 3 January 1911. The shoot-out was not included in Hitchcock's 1956 remake.

Hitchcock hired Australian composer Arthur Benjamin to write a piece of music especially for the set piece at the Royal Albert Hall. The music, known as the Storm Clouds Cantata, is used in both the 1934 version and the 1956 remake.

The film has an approval rating of 88% on Rotten Tomatoes based on 33 reviews, with an average rating of 7.76/10.<!-- The film is not listed on Metacritic. -->

Bans

The film was banned in Norway in January 1935 without citing any reason other than issuing the following statement: The film above is not approved for public viewing in Norway.

The Man Who Knew Too Much is copyrighted worldwide but has been heavily bootlegged on home video. Despite this, various licensed, restored releases have appeared on DVD, Blu-ray and video on demand services from Network Distributing in the UK, Criterion in the US and many others.