Forgotten Realms is a campaign setting for the Dungeons & Dragons (D&D) fantasy role-playing game. Commonly referred to by players and game designers alike as "The Realms", it was created by game designer Ed Greenwood around 1967 as a setting for his childhood stories. Several years later, Greenwood brought the setting to publication for the D&D game as a series of magazine articles, and the first Realms game products were released in 1987. Role-playing game products have been produced for the setting ever since, as have various licensed products including novels, role-playing video game adaptations (including the first massively multiplayer online role-playing game to use graphics), comic books, and the film Dungeons & Dragons: Honor Among Thieves.

Forgotten Realms is a fantasy world setting, described as a world of strange lands, dangerous creatures, and mighty deities, where magic and supernatural phenomena are quite real. The premise is that, long ago, planet Earth and the world of the Forgotten Realms were more closely connected. As time passed, the inhabitants of Earth had mostly forgotten about the existence of that other world – hence the name Forgotten Realms. The original Forgotten Realms logo, which was used until 2000, had small runic letters that read "Herein lie the lost lands" as an allusion to the connection between the two worlds.

Forgotten Realms is one of the most popular D&D settings, largely due to the success of novels by authors such as R. A. Salvatore and numerous role-playing video games, including Pool of Radiance (1988), Eye of the Beholder (1991), Icewind Dale (2000), and the Neverwinter Nights and Baldur's Gate series.