In Which We Serve is a 1942 British patriotic war film directed by Noël Coward and David Lean, who made his debut as a director. It was made during the Second World War with the assistance of the Ministry of Information.

The screenplay by Coward was inspired by the exploits of Captain Lord Louis Mountbatten, who was in command of the destroyer HMS Kelly when it was sunk during the Battle of Crete.

Coward composed the music as well as starring in the film as the ship's captain. The film also starred John Mills, Bernard Miles, Celia Johnson and Richard Attenborough in his first screen role.

In Which We Serve received the full backing of the Ministry of Information, which offered advice on what would make good propaganda and facilitated the release of military personnel. The film is a classic example of wartime British cinema through its patriotic imagery of national unity and social cohesion within the context of the war.