Hiroki Hayashi is a Japanese animator, director, and creator known for his significant contributions to anime original video animations and television series, primarily during the 1990s. He is most closely associated with the studio AIC, where he worked on many of the company's most popular and enduring titles.

Hayashi's career in animation began in the mid-1980s. His early work included storyboard and direction duties on the influential cyberpunk series Bubblegum Crisis, specifically its fourth episode "Revenge Road." His first credit as a director came with the OVA series Sol Bianca, for which he also created the original story concept. The success of these early projects helped establish him as a rising talent within the industry.

His breakout success, and the work for which he is arguably best known, was the first Tenchi Muyo! Ryo-Ohki OVA series in 1992. Hayashi served as the director and co-creator of the original story concept for this series, working alongside Masaki Kajishima. The show, a blend of science fiction, fantasy, and harem comedy, became a landmark title for the industry, spawning a vast multimedia franchise and introducing many international viewers to anime in the 1990s.

Following the triumph of Tenchi Muyo!, Hayashi continued to create original concepts. He was the director and original creator of the first El-Hazard: The Magnificent World OVA series. This fantasy adventure, which shares some thematic and comedic DNA with Tenchi Muyo!, was another major success. He later served as the original creator and series constructor for its television re-imagining, El-Hazard: The Wanderers, which is one of the titles the user specifically mentioned. His creative influence continued to be felt across the El-Hazard franchise, which spawned multiple sequels, though he declined involvement in later OVAs, believing the story had reached its natural conclusion.

Throughout the late 1990s and early 2000s, Hayashi remained a prolific creator and director. He provided the original concept for and directed the television series Battle Athletes, as well as the original concept for Black Heaven. He also took on the role of director for the 1998 television series Bubblegum Crisis Tokyo 2040, a reimagining of the classic OVA he had worked on a decade prior. In 2003, he was the creator and director of the science-fiction comedy Battle Programmer Shirase, the third title mentioned by the user. This series follows a legendary but socially inept hacker, and is noted as a stand-alone story set in the same universe as the Magical Girl Pretty Sammy franchise, which itself is a spin-off of Tenchi Muyo!.

Hayashi's artistic identity is closely tied to the OVA boom of the late 1980s and 1990s, a period that allowed creators significant freedom. His original works often blend genres, mixing science fiction or fantasy settings with ensemble casts, comedic situations, and character-driven plots. He has cited a preference for depicting machines as cool industrial products rather than traditional giant robots, an interest he expressed while working on Bubblegum Crisis. His creative inspirations have been diverse, ranging from the classic sci-fi novel A Princess of Mars, which influenced El-Hazard, to the American sitcom I Dream of Jeannie, which he noted as an inspiration for the character of Ryoko in Tenchi Muyo!. He was also an early adopter of new technology, with his 2001 series Magical Play being his first project to use full 3D computer animation.

Hiroki Hayashi's industry significance lies in his role as a primary creator of several major franchises that defined anime for a generation of fans. Through his directorial work and original concepts for series like Tenchi Muyo! and El-Hazard, he helped establish the commercial and creative template for the popular harem and fantasy comedy genres in anime.