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, with special effects by Yuasa. Produced by Daiei Film, it is the fourth entry in the Gamera film series, and stars Kōjirō Hongō, Tōru Takatsuka, Carl Craig, and Michiko Yaegaki, with Teruo Aragaki as Gamera. In the film, aliens abducts two boy scouts to coerce Gamera to attack Japan.

Gamera vs. Viras was theatrically released in Japan on March 20, 1968. It was followed by Gamera vs. Guiron, released March 21, 1969.