Gigan debuts in the 1972 film Godzilla vs. Gigan, in which it and King Ghidorah are summoned to Earth by the M Space Hunter Nebula aliens, cockroach-like aliens whose planet had been ravaged by another race and wish to subjugate the Earth in order to create a utopia of "perfect peace". However, the monsters are challenged and defeated by Godzilla and Anguirus. In the 1973 film, Godzilla vs. Megalon, Gigan is sent by the Nebulans to assist the people of Seatopia in their assault on humanity by aiding their god, Megalon, in a battle against Godzilla and Jet Jaguar. After having its arm broken by Jet Jaguar however, Gigan retreats into space, leaving Megalon to face Godzilla and Jet Jaguar alone. In the same year, Gigan also makes an appearance in Toho's television series Zone Fighter. After his battle with Godzilla and Jet Jaguar, Gigan is captured by aliens called the Garogans and sent back to Earth to prevent Godzilla from rescuing Zone Fighter. It was temporarily defeated by the former, but revived once Godzilla left and faced Zone Fighter, who eventually killed Gigan.

After a 31-year absence, Gigan returned in the film Godzilla: Final Wars. Millennia prior, it had fought Mothra for the fate of the Earth and was defeated. In the present, its mummified body is discovered in Hokkaido and revealed to be a weapon used by the alien Xiliens, who awaken Gigan to assist them in destroying Earth and destroy the flying battleship the Gotengo to stop its human occupants from awakening Godzilla. While the cyborg disables the battleship, the crew succeed. Gigan faces Godzilla in battle, but is defeated. The Xiliens recover and upgrade Gigan with new weapons to assist Monster X in fighting Godzilla and Mothra. Gigan faces Mothra once more and seemingly kills her, but inadvertently decapitates itself with its razor disks before a burning Mothra destroys it. Gigan returned in Gemstone's GvG and Godzilla vs Gigan Rex, where Godzilla battles an army of soldiers known as Gigan Miles lead by the elite red-colored Gigan Rex.
Created during the early 1970s, when the Godzilla films had undergone a comic book-like shift both in tone and special effects and were now purely science fiction fare, budgets were greatly reduced, so Gigan was designed as both a marketing ploy for children's toys and as a completely alien creature whose design would not have necessitated the same attention to detail needed for Godzilla's previously more earthly opponents.

The character was first conceived by Kaoru Mabuchi in his script Godzilla vs. the Space Monsters – Earth Defense Directive, which contained elements that would later be incorporated into Godzilla vs. Gigan, including having a mind-controlled Gigan teaming up with King Ghidorah, though the script also included Megalon and the mastermind behind the space monsters' actions was a living brain called Miko.

The first Gigan suit was designed by illustrator Takayoshi Mizuki, modeled by suitmaker Noboyuki Yasamaru, and was worn by Kenpachiro Satsuma, who had starred as Hedorah's suit actor in Godzilla vs. Hedorah the year previously. The two initially did not get on well during filming, as Yasamaru focused more on the suit's appearance than on its practicality, at one point making the character's hand-hooks out of pure fiberglass, which made lifting them almost impossible. In portraying Gigan, Satsuma deliberately emphasized the character's destructiv…

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