Hiroyuki Morioka was born on March 2, 1962, in Hyōgo Prefecture, Japan, and is a Japanese science fiction novelist known for creating the expansive Seikai series. Before his career as a writer, he worked as a company employee, first in sales at a publishing company and later at a firm that produced public relations materials, all while writing as a hobby. He graduated from Kyoto Prefectural University with a degree in literature. Morioka made his professional writing debut in 1992 with the short story Yume no Ki ga Tsugeta nara, which had won an honorable mention in the 17th Hayakawa SF Contest in 1991.

Morioka is best known as the original creator of the space opera franchise Crest of the Stars (Seikai no Monshō) and its sequel series Banner of the Stars (Seikai no Senki). The first novel in the series, Teikoku no Ōjo, was published in 1996, and the complete three-volume Crest of the Stars trilogy was released that same year. For this work, he received the prestigious Seiun Award for Best Japanese Novel in 1997. The story follows Jinto Lynn, a human boy who becomes a noble of the Abh Empire, an interstellar civilization of genetically engineered humans with blue hair and a complex constructed language called Baronh, and his relationship with the Abh princess Lafiel. Morioka has stated that his goal is for the entire series to chart the 250-year lifespan of Lafiel from her birth to her ascension to the throne.

The Seikai series has been adapted into multiple anime television productions. The first adaptation was the 13-episode Crest of the Stars in 1999, followed by Banner of the Stars in 2000 and Banner of the Stars II in 2001, for which Morioka is credited as the original novel author. Banner of the Stars II was directed by Yasuchika Nagaoka and produced by the studio Sunrise, airing on WOWOW from July to September 2001. A third anime series, Banner of the Stars III, was released as an original video animation in 2005. Morioka has explained that he was approached by several anime companies after finishing the novels and chose Bandai because their proposal aligned closely with his vision for the series. He has noted that his involvement in the anime adaptations was primarily advisory, pointing out elements incompatible with his character designs while generally allowing the production team creative freedom.

Beyond the Seikai universe, Morioka has written other science fiction and fantasy works. He authored Tsuki to Yami no Senki, a series that incorporates figures from Japanese mythology into a modern setting, as well as the Yasashii Rengoku series about a private investigator in a town inhabited by spirits of the dead. He has also worked in the manga medium, writing Kaze to Tanpopo, a series about three sisters whose peaceful life is disrupted by an alien invasion.

Morioka cites American science fiction writers such as Isaac Asimov and Michael Moorcock as influences, with Asimov's Foundation series particularly inspiring Crest of the Stars. His work is characterized by meticulous world-building, including the creation of the fully developed Baronh language for the Abh species, detailed future histories, and exploration of themes such as cultural identity, imperial politics, and the relationship between different branches of humanity. The Seikai series is considered significant within Japanese science fiction, credited with revitalizing interest in the genre during the late 1990s, and together with Legend of the Galactic Heroes, it is regarded as a representative work of Japanese space opera anime.