They Shall Not Grow Old is a 2018 documentary film directed and produced by Peter Jackson. It was created using footage of the First World War held by the British Imperial War Museum (IWM), most of which was previously unseen, and all of which was over 100 years old by the time of the film's release. Much of the footage was colourised and restored using modern production techniques for its use in the film, and sound effects and voice acting were added to the silent footage. The film's narration was edited from interviews with British WWI veterans from the collections of the BBC and the IWM.

Jackson dedicated the film—his first documentary as director—to his grandfather, who fought in WWI. He said his intention was for the film to be an immersive experience of "what it was like to be a soldier", rather than a story or recounting of events. The crew reviewed 100 hours of archival film footage and 600 hours of interviews with 200 WWI veterans to find the materials from which to construct the film. The film's title was inspired by a line ("They shall grow not old, as we that are left grow old") from Laurence Binyon's 1914 poem "For the Fallen", famous for being used in the "Ode of Remembrance".

The film premiered simultaneously at the BFI London Film Festival and in selected cinemas in the UK on 16 October 2018, before airing on BBC Two on 11 November, the hundredth anniversary of the Armistice of 11 November 1918. In the US, following the success of screenings of the film by Fathom Events on 17 and 27 December, Warner Bros. Pictures gave the film a wide theatrical release in February 2019. Critics acclaimed the film for its restoration work, immersive atmosphere, and portrayal of war.