The "locked-room" or "impossible crime" mystery is a type of crime seen in crime and detective fiction. The crime in question, typically murder, is committed in circumstances under which it appeared impossible for the perpetrator to enter the crime scene, commit the crime, and leave undetected. The crime in question typically involves a situation whereby an intruder could not have left; for example the original literal "locked room": a murder victim found in a windowless room locked from the inside at the time of discovery. Following other conventions of classic detective fiction, the reader is normally presented with the puzzle and all of the clues, and is encouraged to solve the mystery before the solution is revealed in a dramatic climax.

Crime fiction, detective story, murder mystery, mystery novel, and police novel are terms used to describe narratives that centre on criminal acts and especially on the investigation, either by an amateur or a professional detective, of a crime, often a murder. It is usually distinguished from mainstream fiction and other genres such as historical fiction or science fiction, but the boundaries are indistinct. Crime fiction has several subgenres, including detective fiction, courtroom drama, hard-boiled fiction, and legal thrillers. Most crime drama focuses on crime investigation and does not feature the courtroom. Suspense and mystery are key elements that are nearly ubiquitous to the genre.