Detective fiction is a subgenre of crime fiction and mystery fiction in which an investigator or a detective—whether professional, amateur or retired—investigates a crime, often murder. The detective genre began around the same time as speculative fiction and other genre fiction in the mid-nineteenth century and has remained extremely popular, particularly in novels. Some of the most famous heroes of detective fiction include C. Auguste Dupin, Sherlock Holmes, and Hercule Poirot. Juvenile stories featuring The Hardy Boys, Nancy Drew, and The Boxcar Children have also remained in print for several decades.

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.