Hiroyuki Hoshiyama (May 13, 1944 – February 7, 2007) was a prolific Japanese screenwriter whose career spanned over three decades and who played a foundational role in shaping the mecha and real robot genres. While often recognized for his work on the original Mobile Suit Gundam, Hoshiyama was also the original creator behind several significant anime franchises, most notably the Ginga Hyōryū Vifam series.

Hoshiyama entered the animation industry while attending Chuo University, when a friend invited him to visit Mushi Production, the studio founded by Osamu Tezuka. He joined the company, initially working in the art and literature department on drawings before transitioning to scriptwriting. At Mushi Production, he became a colleague of director Yoshiyuki Tomino, a collaboration that would prove highly influential for the industry. Following the bankruptcy of Mushi Production in 1973, Hoshiyama became a freelance writer and began working extensively with Sunrise, Inc., contributing to many of the studio's most important robot anime productions alongside directors such as Tomino, Ryosuke Takahashi, and Takeyuki Kanda.

As an original creator, Hoshiyama is best known for conceiving the Ginga Hyōryū Vifam (Round Vernian Vifam) franchise. The original television series aired in 1983, and Hoshiyama is credited as the original work creator for the entire franchise. This credit extends to the various sequels and spin-offs, including the television sequel Ginga Hyōryū Vifam 13 from 1998, as well as the original video animations Ginga Hyōryū Vifam: Kachua Kara no Tayori, Ginga Hyōryū Vifam: Atsumatta 13-nin, and Ginga Hyōryū Vifam: "Kate no Kioku" Namida no Dakkai Sakusen!! These works all list Hoshiyama as the original creator, establishing him as the architect of that specific science fiction universe.

Beyond the Vifam series, Hoshiyama was also the original creator for Taiyou no Kiba Dougram (Fang of the Sun Dougram), a seminal real robot series from 1981 that emphasized military and political realism. He is further credited as the original concept creator for the compilation film Document Taiyou no Kiba Dougram. In addition to his work as a creator, Hoshiyama frequently served as a series composition writer and scriptwriter on numerous major productions, including Muteki Robo Trider G7, Saikyou Robo Daiohja, City Hunter, Dirty Pair, Future GPX Cyber Formula, Bakusou Kyoudai Let's & Go!! (known as the Spin Fighters or Let's & Go!! series), and the Transformers franchise entries Super-God Masterforce and Victory, for which he served as lead writer and script editor.

Hoshiyama’s writing was marked by a focus on coming-of-age stories and the gradual growth of protagonists who were often flawed but kind-hearted. He was known for his soft-spoken demeanor and for crafting dialogue that was more accessible and emotionally resonant than many of his contemporaries. A student of Italian neorealism, he drew inspiration from European cinema, and his episodes for Mobile Suit Gundam, such as the character-driven story of Kai Shiden, are often cited for their humanistic approach. He also mentored younger screenwriters, including Ichiro Okouchi, who cited Hoshiyama’s work as a direct inspiration for his own career. Hoshiyama passed away in 2007, leaving behind a legacy as one of the most significant scriptwriters and concept creators in the history of Japanese animation, particularly within the robot genre.