Ao Jūmonji is a Japanese light novelist known for creating the Grimgar of Fantasy and Ash series. Born in Hokuto, Hokkaido Prefecture, he is a graduate of the literature department at Hokkaido University. His career began after he received a special prize in the 7th Kadokawa Gakuen Novel Awards in 2003 for his work Jyunketsu Burū Supuringu (Pure Blue Spring). He originally wrote under the pen name Mizore Tōgami but changed it to Ao Jūmonji because the kanji character for Mizore was considered difficult for readers. He made his official debut in 2004 with the first volume of the Bara no Maria (Rose of Maria) series, a prolific fantasy series that would run for 27 volumes. Prior to becoming a writer, Jūmonji worked as a street musician selling his own original music, and he later contributed music to a drama CD adaptation of Bara no Maria under the pseudonym rosen.

Jūmonji is a highly prolific author, having published more than 90 volumes throughout his career and releasing as many as 13 or 14 books in a single year. His body of work consists almost entirely of light novel series and standalone novels, most of which fall within the fantasy genre. Beyond Bara no Maria, other notable series include ANGEL+DIVE, Kuro no Striker, and Sakura x Saku. His most internationally recognized work is Grimgar of Fantasy and Ash, which began publication in 2013. The series was adapted into a manga in 2015 and subsequently into a 12-episode anime television series that aired from January to March 2016. Jūmonji has also contributed to the anime industry in a writing capacity, handling series composition and screenwriting for the 2019 anime Fairy Gone.

His work is characterized by a focus on fantasy settings and the internal struggles of characters, often exploring themes of survival and personal growth within harsh circumstances. The narrative style in Grimgar of Fantasy and Ash, in particular, is noted for its detailed focus on the day-to-day lives and psychological states of its characters. In addition to his original series, he has authored novel adaptations of works by other creators, such as the musical group Sound Horizon.