| Director | Yoshimitsu Banno |
|---|---|
| Budget | ¥100 million |
| Box office | ¥290 million |
Hedorah, an individual of a species of amorphous extraterrestrial alien from the Horsehead Nebula, is transported to Earth by a comet. Upon arrival, it feeds on Earth's pollutants and grows into a poisonous sea monster with the ability to produce sulfuric acid. After it sinks an oil tanker and attacks Dr. Toru Yano and his young son Ken, scarring the doctor, Hedorah's toxic existence is revealed to the public. Ken has visions of Godzilla fighting the world's pollution and insists Godzilla will come to mankind's aid against Hedorah.
Hedorah metamorphoses into an amphibious form, allowing it to move onto land to feed on additional sources of pollution. As Hedorah makes its way to a power station to consume the smoke from its chimneys, it is confronted by Godzilla. Hedorah is easily overpowered by Godzilla and retreats into the ocean. However, during the fight, several pieces of Hedorah's body are flung off, which then crawl back into the sea to grow anew and allow Hedorah to become even more powerful. It returns shortly afterwards in its flying form, then assuming its full form, which demonstrates some of the strongest powers it has access to yet.
Thousands of people across Japan are killed in Hedorah's raids. As hope fades, a party is thrown on Mount Fuji to celebrate one last day of life before the country—and then, the rest of the world—succumbs to Hedorah's unstoppable power. Ken, Yukio Keuchi, Miki Fujinomiya, and the other partygoers realize that Godzilla and Hedorah have also converged on Mount Fuji for a decisive confrontation. During the battle, Godzilla is quickly outmatched by Hedorah's impressive durability and fearsome strength, losing an eye and sustaining a full thickness chemical burn to a hand - right down to the bone - from contact with Hedorah's acidic body and blood, which corrodes anything that comes into contact with it. Finally, Godzilla is almost killed by Hedorah after the alien throws Godzilla into a pit, then attempts to drown Godzilla with a deluge of chemical sludge.
Dr. Toru and his wife Toshie have determined that drying out Hedorah's body may destroy the otherwise unkillable monster. While Godzilla and Hedorah fought, the JSDF swiftly constructed two gigantic electrodes for this purpose and switch them on in an effort to give Godzilla a chance to escape the pit and return to the fight.
Suddenly, the electrodes short out, the power cut off by Godzilla and Hedorah's violent battle. Godzilla reactivates and energizes the electrodes with its atomic breath, which dehydrates Hedorah's exterior. Hedorah's body splits open, and the alien tries to escape using its flying form, but Godzilla propels itself through the air using its atomic breath as a jet to give chase. Godzilla drags Hedorah back to the electrodes and continues to dehydrate it until Hedorah is on the brink of defeat. Godzilla tears open Hedorah's dried-out body and exposes it to the electrodes again, dehydrating pieces of Hedorah's remains until they disintegrate into dust. Godzilla returns to the ocean, but not before pausing to gaze sternly at the surviving humans. Ken bids farewell to Godzilla.