Rei Omishi, also known as Ray Omishi, is a Japanese manga artist and screenwriter recognized for work in the fantasy and comedy genres, particularly during the 1990s. Omishi is best known for illustrating the manga series Sorcerer Hunters, which was adapted into an anime television series. In this capacity, Omishi served as the illustrator for the Sorcerer Hunters manga, while the story was written by collaborator Satoru Akahori. The manga was serialized in Monthly Comic Dengeki Gao! by MediaWorks and published in thirteen volumes between 1993 and 1998. The series was based on a set of light novels, also written by Akahori, and later inspired a twenty-six episode anime adaptation produced by Xebec that aired from 1995 to 1996, as well as a subsequent three-episode original video animation series.

Beyond the Sorcerer Hunters franchise, Omishi is credited as the sole creator of the original manga Omishi Magical Theater: Risky Safety. This series, which Omishi both wrote and illustrated, was serialized in Dengeki Comic Gao! from 1999 to 2000 and collected in three volumes. The story follows an apprentice shinigami named Risky and an apprentice angel named Safety, who are trapped sharing a single body, with their appearance dependent on the emotions of people around them. This manga was also adapted into a twenty-four episode anime series that aired from 1999 to 2000.

Omishi again collaborated with writer Satoru Akahori on the manga Chouse Kitan Maze Bakunetsu Jikuu, also known as Maze, which was serialized in Comic Dragon magazine from 1995 to 1999. Additional manga works attributed to Omishi include Puchi puchi, Crescent Moon, Knight Flyer Tokyo Magic, and Ayakashi ko Tan. Omishi also worked as an illustrator for the series Kaiyou Kiken Seibutsu U-min, based on an original story by Sato o Kou, and contributed to a sequel story titled Sorcerer Hunters: Came Back a Little Bit, written by Akahori. A collection of artwork, Positive Girls! Omishi Rei Gashuu, has also been published.