Hiroya Oku

is a Japanese manga artist, known for his works Hen, Gantz, Inuyashiki, and Gigant, the first two of which have been serialized in Weekly Young Jump. Originally influenced by Katsuhiro Otomo and Ryoichi Ikegami, his manga often contain explicit violence, sexual depictions, and matters that are considered taboo by the public, and he is known as a pioneer in the use of digital processing for manga backgrounds.

His debut manga Hen was a runner-up in the 1988 Young Jump Youth Manga Awards. The pseudonym he used at the time of its serialization was .

Oku designed a character for Namco Bandai's Xbox 360 and PlayStation 3 fighting game Soulcalibur IV, named Shura.

In an August 2026 interview, Oku stated that he would retire after finishing his latest manga series The Sweet Sixty Princess.

Works (1989–1994): published in Shueisha's Weekly Young Jump and collected in 13 volumes. Hen (1995–1997): published in Shueisha's Weekly Young Jump and collected in eight volumes. Zero One (1999–2000): published in Shueisha's Weekly Young Jump and collected in three volumes. Gantz (2000–2013): published in Shueisha's Weekly Young Jump and collected in 37 volumes. (2006–2007): published in Shueisha's Weekly Young Jump and collected in three volumes. (2014–2017): published in Kodansha's Evening and collected in ten volumes. Gantz:G (2015–2017): written by Oku (first volume) and Tomohito Ohsaki (volumes 2 and 3) and illustrated by Keita Iizuka. Published in Shueisha's and Shōnen Jump+ (final chapter only) and collected in three volumes. Gigant (2017–2021): published in Shogakukan's Big Comic Superior and collected in ten volumes. Gantz:E (2020–present): illustrated by Jin Kagetsu. Published in Shueisha's Weekly Young Jump (2020–2023) and YanJan! (since 2024) and collected in nine volumes (as of February 2026). (2025–present): published in Shogakukan's Big Comic Superior and collected in one volume (as of May 2026).