Gamera vs. Guiron (ガメラ対大悪獣ギロン, Gamera tai Daiakujū Giron, lit. Gamera vs. Giant Evil Beast Guiron) is a 1969 Japanese kaiju film directed by Noriaki Yuasa, written by Niisan Takahashi, and produced by Daiei Film.
It is the fifth entry in the Gamera film series, following Gamera vs. Viras, which was released the previous year. Gamera vs. Guiron stars Nobuhiro Kajima, Miyuki Akiyama, Christopher Murphy, Yuko Hamada, and Eiji Funakoshi. The film was released theatrically in Japan on March 21, 1969. It did not receive a theatrical release in the United States, but was released directly to American television that year by American International Television under the title Attack of the Monsters. The film was followed by Gamera vs. Jiger the following year.