The fifth film in the Godzilla franchise and Shōwa series and was the second Godzilla film produced that year; production began following Mothra vs. Godzilla. This film also marks the first appearance of King Ghidorah, a recurring antagonist of the Godzilla franchise. The film was released in Japan on December 20, 1964 and was given a theatrical release in the United States in September 1965 by Continental Distributing as Ghidrah, the Three-Headed Monster.

References:
https://en.wikipedia.org/wiki/Ghidorah_the_Three-Headed_Monster