General Maximus Decimus Meridius leads the Roman army to a decisive victory against the Germanic tribes on the frontier, ending a long war on the Roman frointier and winning the favor of Emperor Marcus Aurelius. The emperor is already old and dying, and although he has a son, Commodus, he asks Maximus to succeed him as a regent and turn Rome back into a republic. The emperor speaks with Commodus afterwards and explains his decision, but Commodus reacts by killing him and caiming the throne.
Maximus manages to escape his own execution by Praetorians and races back to his home in Spain, but he finds his wife and son already dead. A slave caravan passes by and captures Maximus, assuming that he is a deserter. Maximus is forced to fight in local tournaments, and he wins every match. He makes friends with other Proximo's gladiators. His successes allow Proximo to bring the team to the Rome Colosseum. Proximo explains to Maximus that he was himself a gladiator whio fought well enough in the Colosseum to win his freedom, granted to him by Marcus Aurelius himself.
Commodus, desperate to get Maximus out of the way and to restore his own glory, arranges to duel him. Before the fight begins he stabs Maximus in the back, leaving him severely weakened. During the fight, Maximus still manages to dodge Commodus' blows and disarm him. Commodus asks the orders them not to. Commodus produces a hidden stiletto, but Maximus turns the blade back into Commodus' throat, killing him.
Maximus succumbs to the stab wound and dies, asking with his last words that the Roman Republic be restored and that the slaves be freed. As he dies, he has a vision of walking through a field of grain and being finally reunited with his wife and son. Lucilla has the body of Maximus carried out for an honorable burial while the crowd stands in respect. Some time later, Juba revisits the Colosseum at night, and he buries Maximus' two small figurines of his wife and son at the spot where he died. He promises that he will see Maximus again, "but not yet".