The Brain That Wouldn't Die (also known as The Head That Wouldn't Die or The Brain That Couldn't Die) is a 1962 American science fiction horror film directed by Joseph Green and written by Green and Rex Carlton. The film was completed in 1959 under the working title The Black Door but was not theatrically released until May 3, 1962, under its new title as a double feature with Invasion of the Star Creatures.
The film focuses upon a mad doctor who develops a means of keeping human body parts alive. He keeps his fiancée's severed head alive for days, along with a lumbering, malformed brute (one of his earlier failed experiments) imprisoned in a closet.
The specific plot device of a mad doctor who discovers a way to keep a human head alive had been used in fiction earlier (such as Professor Dowell's Head from 1925), as well as other variants on this theme. It shares several key plot devices with the West German horror film The Head (1959).

Dr. Bill Cortner saves a patient who had been pronounced dead, but the senior surgeon, Bill's father, condemns his son's unorthodox methods and theories of transplanting.
While driving to his family's country house, Bill and his beautiful fiancée Jan Compton become involved in a car accident that decapitates her. Bill recovers her severed head and rushes to his country house basement laboratory. He and his crippled assistant Kurt revive the head in a liquid-filled tray. But Jan's new existence is agony, and she begs Bill to let her die. He ignores her pleas, and she grows to resent him.
Bill decides to commit murder to obtain a body for Jan. He hunts for a suitable specimen at a burlesque nightclub, on the streets, and at a beauty contest. Jan begins communicating telepathically with a hideous mutant, an experiment gone wrong, locked in a laboratory cell. When Kurt leaves a hatch in the cell door unlocked, the monster grabs and tears off Kurt's arm. Kurt dies from his injuries.
Bill lures an old girlfriend, figure model Doris Powell, to his house, promising to study her scarred face for plastic surgery. He drugs her and carries her to the laboratory. Jan protests Bill's plan to transplant her head onto Doris's body. He tapes Jan's mouth shut.
When Bill goes to quiet the monster, it grabs Bill through the hatch and breaks the door from its hinges. Their struggles set the laboratory ablaze. The monster, a seven-foot giant with a horribly deformed head, bites a chunk from Bill's right cheek. Bill dies, and the monster carries the unconscious Doris to safety. As the lab goes up in flames, Jan says "I told you to let me die". The screen goes black, followed by Jan's maniacal cackle, welcoming her long-awaited death.