The Ipcress File is a 1965 British spy film directed by Sidney J. Furie, from a screenplay by Bill Canaway and James Doran, based on Len Deighton's 1962 novel The IPCRESS File. It stars Michael Caine as Harry Palmer, an intelligence officer from the War Office investigating the disappearances of high-level scientists.

This film and its sequels were a deliberately downbeat alternative to the hugely successful James Bond films, even though some of the production team were previously involved with the 007 films, including producer Harry Saltzman, production designer Ken Adam, and composer John Barry.

The Ipcress File was released by Rank Film Distributors on 18 March 1965. It received positive reviews and won three BAFTA Awards, including for Best British Film. In 1999, it was included at number 59 on the BFI list of the 100 best British films of the 20th century.

A sequel film, Funeral in Berlin, was released in 1966.

A scientist called Radcliffe is kidnapped from a train and his security escort killed. Harry Palmer, a British Army sergeant with a record of insubordination and a criminal past, now working for a Ministry of Defence organisation, is summoned by his superior, Colonel Ross, and transferred to a section headed by Major Dalby. Ross suspects that Radcliffe's disappearance is connected to the fact that sixteen other top British scientists have inexplicably left their jobs at the peak of their careers. He threatens Dalby that his group will be abolished if Radcliffe cannot be recovered. Palmer is then introduced as a replacement for the dead security escort.

Afterwards, Dalby tells his agents that the main suspects are Eric Grantby and his chief of staff, codenamed "Bluejay" and "Housemartin" respectively, and orders the team to find out where they are at present. Palmer is also introduced to and befriends Jock Carswell. Using a Scotland Yard contact, Palmer locates Grantby but, when Palmer tries to stop Grantby getting away, he is attacked by Housemartin.

Housemartin is arrested later but, before he can be questioned, he is killed by men impersonating Palmer and Carswell. Suspecting that Radcliffe is being held in a certain disused factory, Palmer orders a search, but nothing is found except a piece of audiotape labelled "IPCRESS" that produces meaningless noise when played. Dalby then points out that the paper on which Grantby had written a false phone number is the programme for an upcoming military band concert. There Dalby and Palmer encounter Grantby and a deal is struck for Radcliffe's return.

The exchange goes as planned but, as they are leaving, Palmer shoots a man in the shadows who turns out to be a CIA agent. Subsequently, another CIA operative threatens to kill Palmer if he discovers that the death was not a mistake. Some days later, it becomes clear that while Radcliffe is physically unharmed, his mind has been affected and he can no longer function as a scientist. Carswell has discovered a booklet titled "Induction of Psychoneurosis by Conditioned Reflex under Stress" – IPCRESS – which he believes explains what has happened to Radcliffe and the other scientists. Carswell borrows Palmer's car to test his theory on Radcliffe, but is shot dead before reaching him.