A whodunit is a complex plot-driven variety of detective fiction in which the puzzle regarding who committed the crime is the main focus. The reader or viewer is provided with the clues to the case, from which the identity of the perpetrator may be deduced before the story provides the revelation itself at its climax. The investigation is usually conducted by an eccentric, amateur, or semi-professional detective.

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.