Mystery Dungeon, known in Japan as Fushigi no Dungeon, is a series of roguelike role-playing video games. Most were developed by Chunsoft, now Spike Chunsoft since the merging in 2012, and select games were developed by other companies with Chunsoft's permission. The series began when co–creator of Dragon Quest, Koichi Nakamura, was inspired by Seiichiro Nagahata's experience with Rogue, who is also a fellow developer from the company, and a desire to create an original series. It began on the Super Famicom, progressing to almost all of Nintendo's and Sony's home and handheld consoles, WonderSwan, Dreamcast, Windows, and mobile devices.

The series has inspired other entries in Japan and has moderate popularity, mostly from crossover entries with the Torneko's Great Adventure series in Japan, the Pokémon Mystery Dungeon series worldwide, and lesser with the Chocobo games based on the creatures from the Final Fantasy series. Despite the moderate popularity of the franchise, there have been numerous manga, anime, and novels published under it, whether they are coming from the company's original series, Shiren the Wanderer, or across many crossovers.

The premise of most Mystery Dungeon games is to play a silent protagonist who travels across the world to discover mysterious dungeons that have randomly generated rooms and never have the same patterns upon entering into it more than once, with the protagonist sometimes accompanied by a group of party members or going alone. Though it is relatively inspired of older roguelike games, like NetHack, the franchise had a few unique gameplay elements that would appear in future titles; one such is rescuing other players online via a generated password.