Nisio Isin (西尾 維新 Nishio Ishin), frequently written as NisiOisiN to emphasize that his pen name is a palindrome, is a Japanese novelist and manga writer. He attended and left Ritsumeikan University without graduating. In 2002, he debuted with the novel Kubikiri Cycle, which earned him the 23rd Mephisto Award at twenty years of age.

He currently works with Kodansha on Pandora, the Kodansha Box magazine, and Faust, a literary magazine containing the works of other young authors who similarly take influence from light novels and otaku culture. He was also publishing a twelve volume series over twelve months for the Kodansha Box line; Ryusui Seiryoin was matching this output, and the Kodansha Box website stated that this is the first time in the world two authors have done twelve volume monthly novel series simultaneously from the same publisher.

In February, 2008, his novel Death Note Another Note: The Los Angeles BB Murder Cases was released in English by Viz Media. Del Rey Manga has already released the first volume in his Zaregoto series. His Bakemonogatari, Nisemonogatari and Katanagatari novels have been adapted into anime series. Nekomonogatari (Kuro) has been adapted into an anime TV movie, and Kizumonogatari will be release in theaters this year. Monogatari Series: Second Season, adapted from 6 books in Monogatari Series will air in July 2013. Another of his works, Medaka Box (manga), has been adapted into a two-season anime series.