The Shadow Realm, in the English-language version of the second series Yu-Gi-Oh! anime (titled Yu-Gi-Oh! Duel Monsters in Japan), is a place of eternal suffering where people can be sent to. It is also sometimes used as the site of shadow games.

The Shadow Realm does not exist in the Yu-Gi-Oh! manga and both original Japanese anime series. 4Kids Entertainment, the producer of the English Duel Monsters anime, added in the Shadow Realm. The "Shadow Realm" was often used to write out the real possibility of death or to write out the death of the character; for instance, in the original Japanese manga and Duel Monsters anime, Marik Ishtar's father was killed with a dagger. In the English anime, the father of Marik Ishtar was sent to the Shadow Realm.

Some characters are pulled out of the Shadow Realm in the English anime and the English-language video games.