Masaki Kajishima is a Japanese animator, storyboard artist, and creator best known for his foundational work on the Tenchi Muyo! franchise. Born on March 16, 1962 in Okayama Prefecture, he studied at Osaka Design College and has worked extensively with the animation studio AIC in a freelance capacity. His name is closely associated with the studio, where he has served as a creator, character designer, and supervisor on numerous original video anime (OVA) projects since the early 1990s.

Kajishima first gained prominence as the original creator of Tenchi Muyo! Ryo-Ohki, the original OVA series that began in 1992 and established a long-running multimedia franchise. He is credited as the original creator and original character designer for this series, and has remained involved in its sequels for decades, including the fourth and fifth OVA seasons, where he also serves as chief director. The main character, Tenchi Masaki, was named after Kajishima, though the surname in the character's name is written with different kanji. His work on this franchise extends to its spin-offs, such as the television series Tenchi Muyo! GXP (2002), for which he also wrote a series of light novels beginning in 2003, and its sequel OVA, Tenchi Muyo! GXP Paradise Shidō-hen, where he is credited as supervising director.

In addition to the Tenchi Muyo! universe, Kajishima has created and contributed to several other OVA series. He is the creator of Photon: The Idiot Adventures, a six-episode OVA series released between 1997 and 1999, which he also wrote and for which he provided the original concept. Kajishima was involved in the 1998 OVA Masquerade, where he is credited with writing, original character design, and scenario work. He is also credited as the creator of the OVA Spaceship Agga Ruter, released in 1998-1999. His other noted work includes the television and OVA series Dual! Parallel Trouble Adventure (1999).

Recurring elements within his body of work include a blend of science fiction and comedy, often centered on an everyman protagonist who becomes entangled in intergalactic or supernatural conflicts. A notable theme across several of his series is the concept of an "accidental marriage," where a simple or naive action by the male lead results in a formal bond with a female character, as seen in both Tenchi Muyo! and Photon: The Idiot Adventures. Kajishima is also known for creating interconnected fictional universes; it has been confirmed that the world of Photon is the distant past of the planet Geminar, the setting for the Tenchi Muyo! spin-off War on Geminar.

Masaki Kajishima holds significant importance in the anime industry as the architect of the Tenchi Muyo! franchise, which became a landmark series for the OVA format and helped popularize the harem and space opera genres in the 1990s. His long-standing, multi-decade involvement with the franchise and his consistent collaborations with AIC underscore his role as a key creative figure whose work has had a lasting impact on the industry. Beyond animation, he has also authored novelizations and published collections of doujinshi under the title Kajishima Onsen.