Also, the English title of the first japanese Godzilla/Gojira film, the one that started the legend, series and merchandising spree. Directed by Ishiro Honda, this Toho Studios film was originally released back in November 1954, just a few years after the occupation of Japan after WWII had ended, and any direct mention of the atom bomb was still taboo.
The film opens with an atomic test explosion on a faraway pacific island, setting the logical cause for what is to happen next: 2 merchant ships near Ohto Island in southern Japan are lost under mysterious circumstances as are the rescue ships sent out to find them. When a typhoon ravages Ohto island, killing several inhabitants and others witnessing a monster, the zoologist Dr. Yamane is sent on an fact finding mission to Ohto Island by Japanese government, uncovering that the giant monster does exist. It seems to be a dinosaur from the jurassic period that has survived sleeping in the depths of the ocean, only to be awakened by the bomb tests, which mutated the dinosaur into a giant atomic monster.
The monster is called Gojira by the villagers, who have had encounters with the creature in the past, even going so far as offering maidens to soothe the monster. As attacks on shipping in the Tokyo area continue, the Japanese navy attempts to destroy Gojira using depth charges, which only angers Gojira and directs his wrath towards Tokyo. Gojira quickly defeats the valiantly fighting but finally useless (they don't even manage to wound him) Japanese military forces using its atomic breath, swiftly proceeding to level Tokyo, leaving devastation comparable to the nuclear ruin of Nagasaki and Hiroshima in its wake. The Japanese Air-Force succeeds in driving Gojira back into the bay, but everybody knows that this will only be a brief respite.
Meanwhile, Dr. Yamane's daughter Emiko Yamane discovers that her fiancée, Dr. Serizawa, has developed a weapon he calls the Oxygen Destroyer, which he believes to be capable of destroying Gojira. She begs him to use this weapon to kill Gojira, but he refuses, believing that a horrible weapon like this can never be allowed to be used no matter how just the cause (Hinting that this should have also been the case with the Nukes).
However, seeing the destruction of Tokyo on the TV convinces Dr. Serizawa to agree to the use of the Oxygen Destroyer, insisting to be the one to use it. He proceeds to plant the Oxygen Destroyer near Gojira and and detonates it, while remaining in the water with Gojira. As Godzilla succumbs to the terrible power of the Oxygen Destroyer (A giant bubble bath in the model pool, which somehow turns Gojira into a skeleton), Dr. Serizawa sacrifices himself to prevent his invention to ever be used again by refusing to come up and cutting his oxygen line on the bottom of the sea, having destroyed his records before diving down.