Eiichirō Mashin is a Japanese manga artist and illustrator, known primarily for his work within the Fate franchise. He is the creator of the four-panel comedy manga Himuro no Tenchi Fate/school life, also known as Fate/school life. The series is a spin-off that focuses on the everyday school lives of minor female characters from Fate/stay night, including Kaede Makidera, Kane Himuro, and Yukika Saegusa, at Homurahara Academy. Mashin himself has described the manga as the Sakura Route Ver. 1.5.

Mashin's work gained wider recognition when it was adapted into an animated short. He received the original concept credit for the 2017 anime special Fate/Grand Order x Himuro no Tenchi: 7-nin no Saikyō Ijin-hen (Fate/Grand Order x Himuro's World: Seven Most Powerful Great Figures Chapter). The short, produced by studio ufotable, aired as part of the Fate Project New Year's Eve TV special on December 31, 2017. It is a crossover that incorporates characters and concepts from his manga with the Fate/Grand Order mobile game.

While information about his personal background or other original works remains limited, Mashin is officially recognized as the mangaka of Fate/school life. His contributions to the Fate universe are further evidenced by a reader contest he held for the manga's fifth volume, asking fans to submit designs for the strongest Servant, which he then redrew and compiled.