Gunbuster, known in Japan as Top o Nerae! , is a Japanese OVA anime series produced by Bandai Visual, Victor, and Gainax and released from 1988 to 1989. It was the directorial debut of Hideaki Anno, best known as the creator and director of Neon Genesis Evangelion. The title is a combination of the titles of classic tennis manga and anime Aim for the Ace! and hit action drama film Top Gun, whose plot inspired Gunbuster's. To celebrate Gainax's 20th anniversary in 2004, a sequel to Gunbuster, Diebuster, was released as an OVA. The sequel features new characters and mecha, but retains the format and many of the concepts of the original series.

Gainax Co., Ltd. is a Japanese anime studio famous for productions such as Neon Genesis Evangelion, Royal Space Force, Gunbuster, Nadia: The Secret of Blue Water, Kare Kano, FLCL, Magical Shopping Arcade Abenobashi, and Gurren Lagann, which have garnered critical acclaim and commercial success. Evangelion has reportedly grossed over ¥150 billion, or approximately US$1.2 billion. In a discussion at the 2006 Tekkoshocon, Matt Greenfield claimed that Evangelion had grossed over US$2 billion; Takeda reiterated in 2002 that "It sold record numbers of laserdiscs in Japan, and the DVD is still selling well today", as well as for their association with award-winning anime director and studio co-founder Hideaki Anno. The company is headquartered in Koganei, Tokyo.