Hiroshi Sasagawa is a Japanese animator, manga artist, and director born on July 9, 1936, in Aizuwakamatsu, Fukushima Prefecture. His career in the entertainment industry began in 1958 when he made his debut as a manga artist with the serialization of Detective School in Shōnen Gahōsha. Following this, he gained invaluable experience working as an assistant to Osamu Tezuka, the legendary manga artist often called the "God of Manga." Sasagawa's professional path became closely tied to the animation studio Tatsunoko Production from its very founding, where he became a central and defining figure, particularly during the studio's golden age from the 1970s through the 1980s.

Sasagawa is credited as an original creator on several notable works, with one key example being Oraa Guzura Dado. For this property, he is listed as the creator of the original manga, which was serialized in Weekly Shōnen Sunday in 1967. The manga was based on his own earlier one-shot titled Onboro Kaijū Guzura. The story follows a friendly, metal-eating monster named Guzura who hatches from an egg and causes humorous troubles in the human world. Sasagawa also directed both the original 52-episode anime adaptation that aired on Fuji TV from 1967 to 1968 and a 44-episode remake that aired on TV Tokyo from 1987 to 1988, further cementing his role as the primary author of the franchise.

Beyond this single example, his body of work as a director is extensive and includes many internationally recognized titles. He served as the chief director for the original Speed Racer series, which aired from 1967 to 1968. He is also renowned for his work on the Time Bokan series, a long-running franchise of comedic adventure anime that he helped create. Other significant directorial credits include The Genie Family, Tekkaman: The Space Knight, Ninja Hattori-Kun, and Perman. His career spanned numerous genres, including fantasy and science fiction, but he became particularly celebrated for his mastery of comedy.

Sasagawa's artistic identity is strongly linked to gag humor. He was known for excelling at directing comedic scenes that utilized repetition and was nicknamed the Emperor of Gag Anime. Despite this public persona, he reportedly had a personal preference for more serious, dramatic stories, such as Neo-Human Casshern. His influence extended beyond his own directorial work; he was also a key mentor to a new generation of talent. As a director and head of the directing department at Tatsunoko Production, he initiated a trainee program in 1975 and hired future industry luminaries like Koichi Mashimo, Mizuho Nishikubo, and Mamoru Oshii, who later became known as the Tatsunoko Four Heavenly Kings. He continued to foster new creators at his own personal office, the Hiroshi Sasagawa Office.

His significance to the anime industry is substantial. He was a pillar of Tatsunoko Production during its most influential period and was responsible for shaping the studio's identity, particularly its success with comedic anime. His work on series like Time Bokan and Speed Racer left an indelible mark on popular culture, both in Japan and internationally, and his role as a teacher to future star directors helped sustain the industry for decades. After leaving Tatsunoko in the late 1970s, he remained highly active, working extensively on adaptations of Fujiko Fujio's works throughout the 1980s and early 1990s. His decades-long career makes him a foundational figure in the history of Japanese animation.