Kaiju No. 8 (Japanese: 怪獣8号, Hepburn: Kaijū Hachigō), also known in English as Monster #8, is a Japanese manga series written and illustrated by Naoya Matsumoto. It has been serialized on Shueisha's Shōnen Jump+ online platform since July 2020, with its chapters collected in 15 tankōbon volumes as of March 2025. Shueisha has also published the series digitally on its Manga Plus platform in English and several other languages. Viz Media began publishing the series digitally in August 2020 and has published the series in print in North America since December 2021.