Zettai Muteki Raijin-Oh

Zettai Muteki Raijin-Oh (絶対無敵ライジンオー?, or "Absolutely Invincible Raijin-Oh") is a 51 episode Japanese anime television series, and the first series produced for the Eldran franchise funded by Takara Tomy and produced by Sunrise. It aired in Japan from April 3, 1991 to March 25, 1992. The story revolves around a group of elementary school children who are given command of a mecha named Raijin-Oh and their efforts to defend the Earth from the evil Jaaku (evil) Empire.

There is also a four episode OVA sequel.

Anime Midstream, Inc. announced in December, 2008, that it acquired the license for and planned to release the anime series Zettai Muteki Raijin-Oh in the U.S. sometime in 2009 as their first anime release. The company began selling the first volume of the series direct from their website, as well as several other online retailers as of late December, 2009. The first volume contained episodes 1-5. The second volume, containing episodes 6-10, was released in September 2010, however the series was renamed "Matchless Raijin-Oh" beginning with this volume (and current printings of the first volume are now also marketed under the new title). The third volume was released on July 12, 2011, containing episodes 11-15. Each volume contains English and Japanese audio, as well as special features such as music videos, clean openings/closings, voice bloopers, and the third volume contains an audio commentary with several of the English voice actors.