Kishin Dōji Zenki FX: Vajra Fight (ヴァジュラファイト, lit. "Demon God Child Zenki FX: Vajra Fight") is a side-scrolling action-platform beat 'em up video game developed and published by Hudson Soft exclusively for the PC-FX in Japan on 22 December 1995. It is the fourth title to be based upon Kikuhide Tani and Yoshihiro Kuroiwa's Zenki shōnen manga and anime series, which is based on the Japanese folklore concerning the Great Bodhisattva Jinben Ozunu Enno, and it also has been compared with other titles in the same genre such as Taito's The Ninja Warriors and Treasure's Guardian Heroes. Following the second arc of the manga, which was later adapted into the anime, players assume the role of either Zenki or Chiaki Enno and fight against monsters across several locations in order to rescue a girl named Nozomi and protect Japan from the enemies.
Despite being exclusive to Japan along with the console, Kishin Dōji Zenki FX: Vajra Fight has been met with mixed to positive reception from critics who reviewed it as an import title since its release and was commended for the detailed presentation, colorful visuals and frenetic gameplay. However, its short length was heavily criticized by many. Over the years, the title has since become an expensive collector's item and one of the rarest in the PC-FX library, leading it to fetch high prices in the secondary video game collecting market, in addition to being regarded by publications like Retro Gamer as a standout game on the platform.