On the planet Krypton, Jor-El of the Kryptonian high council discovers the planet will soon be destroyed when its red supergiant sun goes supernova. Despite his insistance, he fails to convince the other council members. To save his infant son, Kal-El, Jor-El launches him in a spaceship to Earth, a planet with a suitable atmosphere where his dense molecular structure will give him superhuman strength and other powers. Shortly after the launch, Krypton's sun explodes, destroying the planet.
The ship crash lands on Earth near Smallville, Kansas. Kal-El, who is now three years old, is found by Jonathan and Martha Kent, who are astonished when he lifts their truck. They take him to their farm and raise him as their own, naming him Clark after Martha's maiden name.
At 18, soon after Jonathan's death from a heart attack, Clark hears a psychic "call" and discovers the glowing green crystal in the remains of his spacecraft. It compels him to travel to the Arctic where it builds the Fortress of Solitude, resembling the architecture of Krypton. Inside, a hologram of Jor-El explains Clark's true origins, and after 12 further years of educating him on his powers and his reason for being sent to Earth, he leaves the Fortress wearing a blue and red suit with the House of El family crest emblazoned on his chest and becomes a reporter at the Daily Planet in Metropolis. He meets and develops an unrequited romantic attraction to coworker Lois Lane.
Lois becomes involved in a helicopter accident where conventional means of rescue are impossible. Clark uses his powers in public for the first time to save her, much to the astonishment of the crowd gathered below. He then goes on to thwart a jewel thief attempting to scale the Solow Building, captures robbers fleeing police through the Fulton Market by depositing their cabin cruiser on Wall Street, and rescuing a girl's cat from a tree in Brooklyn Heights. He also saves Air Force One after a lightning strike destroys the port outboard engine, making the "caped wonder" an instant celebrity. Clark visits Lois at her penthouse apartment the next night and takes her for a flight over the city, allowing her to interview him for an article in which she names him "Superman".
Meanwhile, criminal genius Lex Luthor learns of a joint U.S. Army and U.S. Navy nuclear missile test. He then buys hundreds of acres of worthless desert land out west and reprograms the test's two 500 megaton missiles, one of which to detonate inside of California's largest fault line, the San Andreas Fault, which will cause everything west of the fault to sink into the Pacific Ocean and leave Lex's desert as the new West Coast.
Knowing Superman has the capability stop his plan, Lex deduces that a meteorite found in Addis Ababa is actually part of Krypton and is radioactive to Superman. After he and his accomplices Otis and Eve Teschmacher retrieve a piece of it, Lex lures Superman to his underground lair, reveals his plan and exposes him to a mineral from the meteor piece, Kryptonite, that weakens Superman immediately. Lex further taunts him by revealing the other missile is headed in the eastbound direction toward Hackensack, New Jersey. Teschmacher is horrified because her mother lives in Hackensack, but Lex does not care and leaves Superman to die a slow death. Knowing his reputation for keeping his word, Teschmacher rescues Superman on the condition he will stop the eastbound missile first, Superman reluctantly agrees. Teschmacher frees him from the Kryptonite, then Superman diverts the missile into outer space, consequently preventing him from reaching the other missile in time. The other missile explodes in the San Andreas Fault. Massive earthquakes erupt across California, damaging the Golden Gate Bridge and causing the Hollywood Sign and the Hoover Dam to collapse, endangering lives. Superman mitigates the effects of the explosion, getting rid of the fallout and buildings up the crumbling land in the fault line, preventing the collapse.
While Superman is busy saving others, Lois's car ends up falling into a crevice from one of the aftershocks. It fills with dirt and debris and she suffocates. Angered at being unable to save her, Superman defies Jor-El's earlier warning not to manipulate human history, preferring to heed Jonathan's advice that he must be here for "a reason". He accelerates around Earth, rewinding time, to save Lois. After saving the west coast, he brings Lex and Otis to prison. Then he flies into the sunrise for further adventures.