After imprisoning the Titans beneath the ocean, the Greek gods Zeus and his wife Hera have a son named Hercules. While the other gods are joyful, Zeus' jealous brother Hades plots to overthrow Zeus and rule Mount Olympus. Turning to the Fates for help, Hades learns that in eighteen years, a planetary alignment will allow Hades to locate and free the Titans to conquer Olympus, but only if Hercules does not interfere. Hades sends his minions Pain and Panic to dispose of Hercules. The two succeed at kidnapping and feeding him a formula that turns him mortal, but fail to remove his superhuman strength before Hercules is found and adopted by the farmers Amphitryon and Alcmene.
Years later, the teenaged Hercules becomes an outcast due to his strength, and wonders where he came from. After his foster parents reveal the necklace they found him with, Hercules decides to visit the temple of Zeus for answers. The temple's statue of Zeus comes to life and reveals all to Hercules, telling him that he can regain his godhood by becoming a "true hero". Zeus sends Hercules and his forgotten infant-hood friend Pegasus to find the satyr Philoctetes—"Phil" for short—who is known for training heroes. The two meet Phil, who has retired from training heroes due to numerous disappointments, but Hercules inspires him to follow his dream to train a true hero who will be recognized by the gods. Phil trains Hercules into a potential hero, and when he is older, they fly forThebes. On the way, they meet Megara—"Meg" for short—a sarcastic damsel who Hercules saves from the centaur Nessus. However, after Hercules, Phil, and Pegasus leave, Meg is revealed to be Hades' minion, having sold her soul to him to save an unfaithful lover.
Arriving in Thebes, Hercules finds himself unwanted by the downtrodden citizens until Meg appears, claiming two boys are trapped in a gorge. Hercules saves them, unaware that they are Pain and Panic in disguise, allowing Hades to summon the Hydra to fight Hercules. Hercules continually cuts off its heads, but more heads replace them until Hercules kills the monster by causing a landslide. Hercules is seen as a hero and a celebrity, but Zeus tells Hercules he is not yet a true hero. Driven to depression, Hercules turns to Meg, who is falling in love with him. Hades learns of this and makes a deal with Hercules, to give up his powers for twenty-four hours and Meg will be unharmed. Hercules agrees, losing his strength, and is shocked when Hades reveals that Meg is working for him.
Hades unleashes the Titans who climb Olympus and capture the gods, whilst a Cyclops goes to Thebes to kill Hercules. Phil inspires Hercules to fight and kill the cyclops, but Meg is crushed by a falling pillar saving Hercules from it, allowing him to regain his strength. Hercules and Pegasus fly to Olympus where they free the gods and launch the Titans into space where they explode, though Meg dies before he returns to her. With Meg's soul now Hades' property, Hercules breaks into the Underworld where he negotiates with Hades to free Meg from the Styx in exchange for his own life. His willingness to sacrifice his life restores his godhood and immortality before the life-draining river can kill him, and he rescues Meg and punches Hades into the Styx. After reviving Meg, Hercules and his friends are summoned to Olympus where Zeus and Hera welcome their son home. However, Hercules decides to remain on Earth with Meg with his parents' blessing. Hercules returns to Thebes where he is hailed as a true hero as Zeus creates a picture of Hercules in the stars commemorating his heroism.