In AD 180, Hispano-Roman General Maximus Decimus Meridius leads the Roman army to a decisive victory against the Germanictribes near Vindobona, ending a long war on the Roman frontier and winning the favor of the Emperor Marcus Aurelius. Maximus, weary of battle, desires to retire to his Spanish farm estate, but the Emperor tells him that his own son and heir to the throne, Commodus, is unfit to rule and so appoints Maximus as regent to help save Rome from corruption. Before Maximus makes his decision, Commodus is confronted by his father who tells him that he will not be emperor. Burdened by grief and believing he was never valued by his father, Commodus murders him.
After mourning Marcus Aurelius’ death, the new Emperor asks Maximus for his loyalty, but the general suspects foul play and refuses. Soon after, Maximus is arrested and is scheduled to be executed at dawn. Maximus manages to escape and makes the long journey to his farm on horseback, but arrives to find it burnt and his family dead, under orders of Commodus. He buries them and collapses in despair. He is then captured by slavers who take him toZucchabar, a North African province. He is sold to a man named Proximo, who trains him as a gladiator. There he befriends two of Proximo’s gladiators, a Numidian named Juba and a German named Hagen.
Reluctant at first, Maximus is forced to fight in local tournaments. He wins every match because of his superior military skills and traumatized indifference to death. His newfound fame and recognition is brought to Proximo’s attention. Proximo reveals to Maximus that he himself was once a gladiator, and had fought well enough to have gained his freedom. He encourages Maximus to go to Rome and fight in the Colosseum, where the Emperor has organized 150 days of games to commemorate his late father. Proximo advises him to “win the crowd” to earn their respect and eventually his freedom. He could then use this leverage to possibly overthrow or kill the Emperor as part of his plan for revenge.
Maximus’ first taste of gladiatorial combat in the Colosseum is depicted as a re-enactment of the Battle of Zama. With his team portrayed as Carthaginian infantry, they defy all expectations and are able (solely due to Maximus’ commands) to defeat “Scipio’s legionaries” who were supposed to obliterate them. A surprised and delighted Commodus comes into the arena to personally congratulate them. Maximus braces himself to kill the Emperor, but at the last moment decides against it because of the presence of Commodus’ young nephew Lucius Verus. He then reveals himself to the startled Commodus and vows to have his vengeance. As the Praetorian Guard prepares to kill him, the crowd chants “Live!” repeatedly, earning their favor and showing their support. Commodus relents and leaves angrily.
Next, Maximus is pitted against the formidable Tigris of Gaul, an undefeated gladiator. After a fierce and lengthy duel which Commodus attempted to fix, Maximus is able to gain the upper hand, but spares his opponent’s life despite the crowd’s urging that he kill him. Angered by this action, Commodus berates him, even taunting him with harrowing details of his family’s death. Undaunted, Maximus turns around and walks away. This act of defiance, along with his victory over Tigris, makes him more popular than the Emperor himself.
As Maximus is being escorted back to the gladiators’ quarters, his former orderly Cicero approaches him and says that he still has the loyalty of the legions, encamped near Rome. Commodus’ sister Lucilla and the chief senator Gracchus secure a meeting with Maximus, and he obtains their promise to help him escape Rome, rejoin his soldiers, topple Commodus by force, and hand power over back to the Senate. Suspicious, Commodus learns of this plot from Lucilla by threatening young Lucius, then dispatches his men to arrest and/or kill the conspirators. Gracchus is quickly apprehended, while a contingent of Praetorians is sent to Maximus’ quarters. Proximo lets Maximus escape and sacrifices himself and his men (including Hagen) to gain him more time. Maximus reaches the rendezvous point but falls into a trap; Cicero is killed and Maximus is captured.
Commodus, desperate and jealous of Maximus’ growing popularity, challenges him to a duel in the Colosseum. Before the fight, and unknown to the crowd, he stabs him in the side to put him at a disadvantage. During the fight, Maximus manages to evade Commodus’ blows and disarm him. Commodus asks the Praetorians to give him a sword, but his request is denied. He produces a hidden stiletto, but Maximus instinctively turns the blade back into his throat, killing him.
However, Maximus succumbs to the stab wound, asking with his last words that reforms be made, his gladiator allies freed, and that Senator Gracchus be reinstated. He is then carried away for an honorable funeral as a “soldier of Rome”. Later, Juba revisits the Colosseum at night, and he buries Maximus’ figurines of his wife and son at the spot where he died. He promises that he will see Maximus again, “but not yet”.