In 1757 during the French and Indian War, the British and French are battling for control of North America. Though they are bound by law to join the militia to aid the British, many settlers are reluctant to leave their frontier homes and families defenseless against Huron Indians allied with the French.
Hawkeye (Daniel Day-Lewis), Chingachgook (Russell Means), and Uncas (Eric Schweig), the last of the Mohican tribe, visit the Cameron household. Jack Winthrop joins them and tells Hawkeye that he is gathering volunteers for the British army. The next morning, Jack and a group of others go to Albany to obtain terms from General Webb, who agrees to grant them leave if their homes are attacked. Satisfied, the volunteers join the British forces at Fort William Henry, north of Albany, New York.
Cora Munro (Madeleine Stowe) and her sister Alice (Jodhi May) have received word from their father, Colonel Edmund Munro (Maurice Roëves), the commander of the British garrison at the fort, to meet him there. A native guide named Magua (Wes Studi) and a detachment of British soldiers commanded by Major Duncan Heyward (Steven Waddington) escort the women on the trail. However, they are ambushed by Hurons led by Magua himself. All of the soldiers except Heyward are quickly killed. He, Cora and Alice are rescued by Hawkeye and his companions, who have been tracking the war band. Magua prepares to shoot Cora, but Hawkeye distracts him. With the rest of his men dead, Magua flees into the forest. The rescuers reluctantly agree to escort the survivors to Fort William Henry. Along the way, they discover that the Cameron homestead has been razed and everyone killed, though nothing has been stolen, a sure sign of a war party.
When they arrive at Fort William Henry, they find it under siege by the French. They manage to sneak inside. When Munro scolds his daughters for joining him, they realize that Magua has deceived them for unknown reasons. Munro tells Heyward that the fort can only hold out for three more days. Their only hope is to get a messenger through to General Webb at nearby Fort Edward for reinforcements.
Hawkeye tells the colonel and the colonials about the attack on the Camerons and the colonials demand that he release them to defend their homes, as General Webb agreed. Munro refuses, so Hawkeye covers for Jack and his friends so they can desert. Hawkeye, who stays behind to be with Cora, is arrested for sedition and sentenced to hang.
Several days pass. As the fort is on the verge of falling, the French commander, General Montcalm (Patrice Chéreau) offers Munro surrender terms, presenting a letter from General Webb that he can’t spare any forces. The garrison and their families are offered safe passage to Albany, on condition they return to England and no longer fight in the war. Munro reluctantly accepts, after Montcalm shows him an intercepted message that Webb has refused to send aid.
As the British march away, they are ambushed by a much larger force of Hurons led by Magua. Before Magua kills Munro, he tells him he will kill the colonel’s daughters so that his family will be extinguished; he then cuts out Munro’s heart. Earlier, it is revealed that Magua’s village had been destroyed years ago by British soldiers led by Munro, resulting in the death of his children and his wife marrying another man when she thought Magua was dead. Magua himself was made a slave.
Hawkeye, Cora, Alice, Uncas, Chingachgook, Heyward and two other soldiers escape and hide in a cave behind a waterfall, but Magua and his men are close behind. With their gunpowder wet, Hawkeye and his two companions jump into the falls, knowing their presence would precipitate a hopeless fight. Heyward and the two women are captured while the remaining soldiers are quickly dispatched.
The prisoners are taken to a Huron village, with Hawkeye, Uncas and Chingachgook in pursuit. Magua is bargaining with the sachem when they are interrupted by the arrival of an unarmed Hawkeye running the gauntlet of hostile warriors. With Heyward translating, Hawkeye convinces the chief that Magua is acting for himself, rather than the Hurons’ best interests and traditions. The chief agrees and renders his judgment: Cora is to be burned alive to atone for Magua’s dead children; Magua is given Alice to be his wife so that both bloodlines can continue; and Heyward is to be returned to the British in the hope of avoiding reprisals. Hawkeye is given safe passage in recognition of his bravery. Desperate, he demands they take him in Cora’s place. Heyward, out of love for Cora and newfound respect for Hawkeye, deliberately mistranslates, offering himself instead. When the chief accepts, Magua curses him and leaves with Alice and his men.
Uncas immediately follows the war band, while Chingachgook waits for Hawkeye. From a safe distance, Hawkeye shoots Heyward, ending his suffering. They then set off in pursuit of Magua.
Uncas catches up with Magua’s band alone. He kills several men before engaging Magua in single combat. Magua kills Uncas, dropping his body off a cliff. Alice then throws herself after him. A devastated Hawkeye, Chingachgook and Cora witness their deaths from a distance. Finally catching up, the two men slay several warriors. As Hawkeye holds the rest at bay, Chingachgook fights Magua and avenges his son.
In the final scene, Chingachgook and Hawkeye engage in a spiritual ritual to send Uncas’ spirit to his ancestors. With the death of Uncas, his last blood relative, Chingachgook names himself ‘the last of the Mohicans’.