Gamera vs. Viras (ガメラ対宇宙怪獣バイラス, Gamera tai Uchū Kaijū Bairasu, lit. Gamera vs. Outer Space Monster Viras) is a 1968 Japanese kaiju film directed by Noriaki Yuasa, written by Niisan Takahashi, and produced by Daiei Film. It stars Kōjirō Hongō, Tōru Takatsuka, Carl Craig, and Michiko Yaegaki, and is the fourth entry in the Gamera film series, after the previous year’s Gamera vs. Gyaos. The film also features Teruo Aragaki as the giant flying turtle monster Gamera, and introduces the extraterrestrial monster Viras.

Gamera vs. Viras was released theatrically in Japan on March 20, 1968. It did not receive a theatrical release in the United States, instead being released directly to television by American International Television in 1969, under the title Destroy All Planets. The film was followed by Gamera vs. Guiron the following year.