Kenichi: The Mightiest Disciple (史上最強の弟子ケンイチ Shijō Saikyō no Deshi Ken'ichi?, lit. History's Strongest Disciple Kenichi) is a Japanese manga by Syun Matsuena serialized in the weekly manga magazine Shōnen Sunday.
 
This manga is a remake of Tatakae! Ryōzanpaku Shijō Saikyō no Deshi (戦え!梁山泊 史上最強の弟子?, lit. Fight! Ryōzanpaku, History's Strongest Disciple), which was serialized in the monthly manga magazine Shōnen Sunday Super, publishing five tankōbon between 2000 and 2002.
 
The first tankōbon was published on August 9, 2002. An anime adaptation by Tokyo Movie Shinsha aired 50 episodes from October 2006 to September 2007. Brain's Base is producing OVAs, which continue from the Ragnarok Arc. The first OVA was released on March 14, 2012, the second OVA was released on June 18, 2012, and a third OVA will be released on November 16, 2012.

The story focuses on Kenichi Shirahama, an average 17-year-old high school student who has been picked on his whole life. However, on his first day of class, he meets and befriends the mysterious transfer student, Miu Fūrinji. Driven by his desire to become stronger and to protect those around him, he follows her to Ryōzanpaku, a dojo where those who are truly strong and have mastered their arts gather (Ryōzanpaku comes from the Chinese story of Heroes of the Water Margin who train together at Liangshan ). After learning basics from Miu, Kenichi is able to beat a high-ranking member of the school's karate club, and becomes a target for all the delinquents in the school. Kenichi's reason for training is to fulfill the promise he made to protect Miu. Subsequently, Kenichi's daily routine is divided between hellish training under the six masters of Ryōzanpaku, and his fights against the members of Ragnarok, a gang that views him as either a possible ally or an impending threat to their plans.
 
After defeating Ragnarok, Kenichi faces a new enemy called Yomi, a group of disciples who are each personally trained by a master of an even bigger organization rivaling Ryōzanpaku, Yami. While the masters of Ryōzanpaku follow the principle of always sparing their opponents' lives (Katsujin-ken), the members of Yami believe that defeating an opponent is valid by any means including murder (Satsujin-ken). Caught in the struggle between the two factions, Kenichi, Miu and their ever growing team of allies join forces to fight the members of Yomi, while his masters confront the members of Yami in a battle to decide the future of the martial arts' world.