Gate Keepers (ゲートキーパーズ, Gēto Kīpāzu?) is a Japanese manga series written by Hiroshi Yamaguchi and drawn by Keiji Gotoh in 1999. The manga was adapted into anime series produced by Gonzo, and first aired on April 3, 2000. The series was also produced into a role-playing game for PlayStation.
A six episode OVA sequel Gate Keepers 21, was released in 2002. The main characters in the OVA sequel were the next generation of Gate Keepers.
All incarnations of the titled "Gate Keepers" series, follow the same basic premise and share most of their characters, with some major discrepancies (mainly involving the character Reiji Kageyama). A character from the game, Francine Allumage is completely absent from the anime. Another character from the game Misao Sakamori, was replaced in the anime with the new original character Megumi Kurogane (though Misao does make a guest appearance towards the end of the anime).