In the Dungeons & Dragons (D&D) role-playing game, the Dungeon Master (often abbreviated as DM) is the game organizer and participant in charge of creating the details and challenges of a given adventure, while maintaining a realistic continuity of events. In effect, the Dungeon Master controls all aspects of the game, except for the actions of the player characters, (PCs) and describes to the other players what they see and hear.

The title was invented for the TSR Dungeons & Dragons RPG, and was introduced in the second supplement to the game rules (Blackmoor). To avoid infringement of TSR's trademarks, and to describe referees in role-playing genres other than sword and sorcery, other gaming companies use more generic, terms, like Game Master, Game Operations Director, Judge, Referee or Storyteller, with some using more esoteric titles related to the genre or style of the game, such as Keeper of Arcane Lore, or even completely surreal titles such as Hollyhock God.

Also, in Faiths and Pantheons, the Faerunian Overgod Ao answers to a superior entity, insinuated to be the "Dungeon Master".