Bunny Lake Is Missing is a 1965 psychological thriller mystery film directed and produced by Otto Preminger and starring Carol Lynley, Keir Dullea, and Laurence Olivier. Adapted from the 1957 novel of the same name by American writer Merriam Modell, the film follows a woman who reports her young daughter as missing, despite the fact that there seems to be no evidence she ever existed.

A co-production between the United Kingdom and United States, Bunny Lake Is Missing was adapted from Modell's novel by screenwriters John and Penelope Mortimer. While the novel is set in New York City, Preminger and the Mortimers altered the film's location to London, where the film was shot on location in early 1965. The score is by Paul Glass, and the British rock band the Zombies also appear in the film.

Bunny Lake Is Missing had its world premiere in New York City on 3 October 1965, with a British theatrical release following on 27 February 1966. The film received generally positive reviews from critics, and was nominated for two BAFTA Awards, in the categories of Best Art Direction and Best Cinematography.

American single mother Ann Lake, who recently moved to London from New York, arrives at the Little People's Garden preschool to collect her daughter, Bunny. The child has mysteriously disappeared. An administrator recalls meeting Ann but claims never to have seen the missing child. Pressed to be back home in time for an appointment with the movers, Ann had been unable to wait to hand Bunny over in person to the administrator; she had been instructed by another employee to leave Bunny in a waiting room with another child and parent. Ann and her brother Steven search the school and find a peculiar old woman living upstairs, who claims she collects children's nightmares. In desperation, the Lakes call the police, and Superintendent Newhouse arrives on the scene. Everyone becomes a suspect, and Superintendent Newhouse is steadfast, diligently following every lead. Newhouse and the police decide to visit the Lakes' new residence.

All of Bunny's possessions have been removed from the Lakes' new home. Ann cannot understand why anyone would do this and reacts emotionally. Superintendent Newhouse begins to suspect that Bunny Lake does not exist, particularly after Steven informs him that "Bunny" was the name of Ann's imaginary childhood friend. Hoping to verify Bunny's existence on the manifest, Newhouse asks Steven for the name of the ship on which Ann and Bunny were passengers on the trip to England. Steven argues with Newhouse, angrily asserting that he will hire a private detective to find Bunny, and storms off. Deciding to become better acquainted with Ann to learn more about Bunny, Newhouse takes Ann to a local pub where he plies her with brandy and soda.

On her return home, Ann discovers she still has the claim ticket for Bunny's doll, which she had taken to a doll hospital for repairs. Regarding the doll as proof of Bunny's existence, she frantically rushes to the doll hospital late at night and retrieves the doll. When Ann shows Steven the doll, affirming that the doll’s existence proves Bunny’s existence, Steven takes the doll and sets it on fire, hoping to destroy it, then knocks Ann unconscious. Steven takes the unconscious Ann to a hospital, informing the desk nurse that Ann has been hallucinating about a missing girl who does not exist. Ann is put under observation with instructions for her to be sedated if she awakes.

Ann wakes up in the hospital and escapes. Discovering Steven burying Bunny's possessions in the garden, Ann then finds a bound and gagged Bunny, who Steven had taken from the preschool, sedated, and hidden in the trunk of his car. Steven reveals an incestuous interest with his sister, complaining that Bunny has always come between them, starting with when Ann became pregnant from a relationship with her boyfriend. Resenting that Ann loves Bunny more than him, Steven wishes to eliminate Bunny, who threatens his dream of a future with his sister.

Realizing her brother is insane, Ann begins playing childhood games with Steven, hoping to distract him from killing Bunny and to facilitate their escape. Reverting back to childhood interaction, Ann demands that they play Hide and Seek, with Steven being blindfolded while Ann and Bunny "hide." While Steven is blindfolded and counting, Ann and Bunny run to escape, but soon Steven is done counting and begins the chase. Unable to outrun Steven, Ann and Bunny attempt to hide, with Ann locking Bunny in a greenhouse and attempting to misdirect Steven away from her. Ann's attempt to secure Bunny fails when she discovers that Steven had hidden in the greenhouse and has captured Bunny. Desperate to distract Steven, and playing for time, Ann insists that she's bored with hide and seek and demands that Steven push her higher and higher on the nearby swing set. Enthralled by his sister's attention, Steven temporarily loses focus on Bunny.