The initial series of movies to feature the fictional kaiju character Godzilla. Much of the Shōwa series monster-action was intentionally made comical and laughable for children, with Godzilla frequently engaged in clownish slapstick wrestling with other monsters.
Two pilots named Shoichi Tsukioka and Koji Kobayashi are hunting for schools of fish for a tuna cannery company in Osaka. Kobayashi's plane malfunctions and is forced to land near Iwato Island, an uninhabited strip of rocks formed by volcanic eruptions. Tsukioka then looks for Kobayashi and finds him safe, with only a wrist sprain. While talking, the two men hear some strange sounds and find two monsters fighting. Tsukioka immediately recognizes one of the monsters to be Godzilla. The two monsters then fall off a cliff, into the ocean.
Mr. Tako, head of Pacific Pharmaceuticals, is frustrated with the television shows his company is sponsoring and wants something to boost his ratings. When a doctor tells Tako about a giant monster he discovered on the small Faro Island, Tako believes that it would be a brilliant idea to use the monster to gain publicity. Tako immediately sends two men, Sakurai and Kinsaburo, to find and bring back the monster. Meanwhile, the American submarine ''Seahawk'' gets caught in an iceberg. The iceberg collapses, unleashing Godzilla (who, in the Japanese version, had been trapped within since Godzilla Raids Again), who then destroys the submarine and a nearby Arctic military base.
Mothra's egg washes ashore and is claimed by greedy entrepreneurs who refuse to return it to her fairies. As Godzilla arises near Nagoya, the people of Infant Island must decide if they are willing to answer Japan's own pleas for help.
In the year 196X, two astronauts, Fuji and Glenn, are sent to investigate the surface of the mysterious "Planet X". There they encounter advanced and seemingly benevolent human-like beings called the Xiliens and their leader the Controller. The aliens usher the astronauts into their underground base, and moments later the surface is attacked by a creature the Xiliens call "Monster Zero", but which the astronauts recognize as King Ghidorah, a planet-destroying monster that had attacked Earth once before. The monster eventually leaves, but the Controller states that Ghidorah has been attacking repeatedly, forcing them to live underground in constant fear. He requests to borrow the Earth monsters Godzilla and Rodan to act as sentries against Ghidorah's attacks, in return for the cure for cancer (the English dub says the formula can cure any disease). The astronauts return to Earth and deliver the message.
A young man steals a boat to find his brother, but he and his shipmates become shipwrecked on a mysterious island inhabited by a giant sea monster and a slumbering Godzilla.
A team of scientists are trying to perfect a weather-controlling system. Their efforts are hampered by the arrival of a nosy reporter and by the sudden presence of 2-meter tall giant praying mantises. The first test of the weather control system goes awry when the remote control for a radioactive balloon is jammed by an unexplained signal coming from the center of the island. The balloon detonates prematurely, creating a radioactive storm that causes the giant mantises to grow to enormous sizes. Investigating the mantises, which are named Kamacuras (Gimantis in the English-dubbed version), the scientists find the monstrous insects digging an egg out from under a pile of earth. The egg hatches, revealing a baby Godzilla. The scientists realize that the baby's telepathic cries for help were the cause of the interference that ruined their experiment. Shortly afterwards, Godzilla arrives on the island in response to the infant's cries, demolishing the scientist's base while rushing to defend the baby. Godzilla kills two of the Kamacuras during the battle while one manages to fly away to safety, Godzilla then adopts the baby.
At the close of the 20th century, all of the Earth's kaiju have been collected by the United Nations Science Committee and confined in an area known as Monsterland and Monster Island, located in the Ogasawara Islands. A special control center is constructed underneath the island to ensure that the monsters stay secure and to serve as a research facility to study them.
Ichiro Miki (Tomonori Yazaki) is a highly imaginative but lonely latchkey kid growing up in urban (and at that time, polluted) Kawasaki, Kanagawa. Every day he comes home to his family's empty apartment. His only friends are a toymaker named Shinpei Inami (Eisei Amamoto) and a young girl named Sachiko (Hidemi Ito). Every day after school, Ichiro is tormented by a gang of bullies led by a child named Sanko Gabara (Junichi Ito). To escape his loneliness, Ichiro sleeps and dreams about visiting Monster Island. During his visit, he witnesses Godzilla Son of Godzilla and Ebirah, a giant sea monster. Ichiro is then chased by a rogue Kamacuras and falls into a deep cave, but luckily avoids being caught by Kamacuras. Shortly afterward, Ichiro is rescued from the cave by Minilla. Ichiro quickly learns that Minilla has bully problems too, as he is bullied by a monstrous ogre known as Gabara.
The microscopic alien life-form Hedorah feeds on Earth's pollution and grows into a poisonous, acid-secreting sea monster. After it sinks an oil tanker and attacks Dr. Toru Yano and his young son Ken Yano, scarring the doctor, Hedorah's toxic existence is revealed to the public. Ken Yano has visions of Godzilla fighting the world's pollution and insists Godzilla will come to humankind's aid against Hedorah.
Giant insectoid aliens resembling cockroaches from a dying planet in "Space Hunter Nebula M" plot to colonize the Earth. The aliens assume the forms of dead humans and work as the development staff of the peace-themed Amusement park, World Children's Land, the centerpiece of which is "Godzilla Tower". The Nebula M aliens plan to use the space monsters Gigan and King Ghidorah, guided by two "Action Signal Tapes", to wipe out human civilization.
The undersea nation of Seatopia sends the gigantic Megalon to destroy the world above - and it's up to Godzilla and a size-shifting robot, Jet Jaguar, to defeat him.
Strange events are taking place in Okinawa. An Azumi people priestess has a terrifying vision of a city being destroyed by a giant monster. A type of metal not found on earth is discovered in a cave by a spelunker, Masahiko Shimizu, who takes it to Professor Miyajima for examination. An excavation led by Masahiko's brother Keisuke accidentally uncovers a chamber filled with ancient artifacts and a mural bearing an ominous prophecy: "''When a black mountain appears above the clouds, a huge monster will arise and try to destroy the world; but then, when the red moon sets and the sun rises in the west, two more shall appear to save humanity.''" Keisuke is joined by archaeologist Saeko Kaneshiro, who translates the prophecy and takes one of the artefacts, bearing the likeness of the legendary monster King Caesar, to study. Two men stalk them, one who speaks to them and claims to be a reporter interested in the story, the other of whom attempts to steal the statue from them but fails and flees.
Continuing after the end of the events of ''Godzilla vs. Mechagodzilla'', Interpol agents, led by Inspector Kusaka, search for the pieces of Mechagodzilla at the bottom of the Okinawan Sea. Using the submarine, ''Akatsuki'', they hope to gather information on the robot's builders, the alien Simeons. The ''Akatsuki'' is suddenly attacked by a giant aquatic dinosaur called Titanosaurus (Godzilla) and the crew vanishes.