The neck riddle is a riddle where the riddler (typically a hero in a folk tale) gains something with the help of an unsolvable riddle. Verlyn Flieger (citing Williamson, Archer Taylor and Hilda Ellis Davidson) defines neck riddles as "questions that are unanswerable except by the asker, who thus saves his neck by the riddle, for the judge or executioner has promised release in exchange for a riddle that cannot be guessed".
The name comes from the folk tales of type "Out-riddling the judge" (Aarne–Thompson classification system for folk tales #927), when the hero "saves his neck" (that is, avoids being sentenced to a death by hanging) after outwitting a judge with riddles.