On the far away planet of Krypton, scientist Jor-El (MARLON BRANDO), having just sentenced the treasonous Gen. Zod (TERRENCE STAMP) and his co-conspirators to a space-based purgatory, now worries about his planet and his young son. With the leading council to which he belongs denouncing his doomsday predictions, Jor-El and his wife place their infant in a specialized spaceship, complete with crystals of knowledge that will educate him, and send him on a several-year journey to Earth. Although it's a more primitive planet than theirs is, the boy will look human and thus fit in, but his molecular structure will provide him with great powers.
The now toddler-aged boy ends up in the caring hands of Jonathan (GLENN FORD) and Martha Kent (PHYLLIS THAXTER), who name him Clark and instill basic Midwestern values in him, that include not showing off with his superhuman abilities. When his father dies, Clark heads off to the arctic where he receives years of training and learning from a sentient representation of the now long-dead Jor-El.
With his education complete, Clark emerges as Superman (CHRISTOPHER REEVE), a superhero destined to protect the innocent and defeat the bad guys of the world. Using his mild-mannered alter ego, Clark gets a job in Metropolis as a reporter for the Daily Planet where he works with fellow reporter Lois Lane (MARGOT KIDDER) and young photographer Jimmy Olsen (MARC McCLURE) for editor Perry White (JACKIE COOPER).
When sightings of Superman start erupting around the city, White wants his team to get the scoop on the man of steel, a point that leads to some potential romantic feelings between Superman and Lois. Yet, the superhero doesn't have time for that as criminal mastermind Lex Luthor (GENE HACKMAN) has a devious, money-making scheme up his sleeves. After reprogramming two nuclear missiles with the aid of Miss Teschmacher (VALERIE PERRINE) and the dimwitted Otis (NED BEATTY), Luthor plans to blast the west coast into the sea, thus turning him and his newly acquired border real estate golden.
With time running out and many lives at risk, Superman then races to stop the madman and his plan.