SinIchi Hiromoto is a Japanese manga artist and character designer born on January 3, 1966, in Kumamoto Prefecture. He began his professional career in the early 1990s, with his debut work, Single Action Army, serialized in Kodanshas Monthly Afternoon magazine from 1992 to 1993.

Hiromoto is the original creator of the manga Hells Angels, which was serialized in Shueishas seinen magazine Ultra Jump from August 19, 2002, to April 19, 2004. The series was compiled into three tankōbon volumes and blends comedy, horror, and supernatural themes, following a high school girl navigating life in a demonic academy after her death. This manga served as the source material for the anime film Hells, produced by Madhouse and directed by Yoshinobu Yamakawa, which premiered at the 2008 Tokyo International Film Festival.

Beyond Hells Angels, Hiromoto has created a substantial body of work known for its boundary-pushing seinen narratives that fuse horror, high-octane action, and surreal absurdity. His notable original manga series include STONe, Bushidou, and Life + Scarlet (Inochi + Kurenai). He has also worked on established franchises, serving as the artist for the manga adaptation of Star Wars: Return of the Jedi and contributing to the Neo Devilman series. His artistic style is characterized by intricate and often grotesque linework, designed to depict visceral action and satirical themes.

In the video game industry, Hiromoto worked as the character designer and art director for the Nintendo GameCube titles Pokémon Colosseum and its sequel, Pokémon XD: Gale of Darkness. He was also credited under the name Hiromoto SINIchi in the credits for Super Smash Bros. Melee.