Night Mail is a 1936 British documentary film directed and produced by Harry Watt and Basil Wright, and produced by the General Post Office (GPO) Film Unit. The 24-minute film documents the nightly postal train operated by the London, Midland and Scottish Railway (LMS) from London to Scotland and the staff who operate it. Narrated by John Grierson and Stuart Legg, the film ends with a "verse commentary" written by W. H. Auden to a score composed by Benjamin Britten. The locomotive featured in the film is LMS Royal Scot Class 6115 Scots Guardsman.

Night Mail premiered on 4 February 1936 at the Cambridge Arts Theatre in Cambridge, England in a launch programme for the venue. Its general release gained critical praise and became a classic of its own kind, much imitated by adverts and modern film shorts. Night Mail is widely considered a masterpiece of the British Documentary Film Movement. A sequel was released in 1987, entitled Night Mail 2.