In the year
2154, Jake Sully (
Sam Worthington), a former
U.S. Marine paralyzed from the waist down due to wounds sustained in combat, is selected to participate in the Avatar program. Originally, the position was supposed to be filled by his identical twin brother Tom, but he was recently killed in action. Arriving from the six-year journey from
Earth to Pandora, Jake awakes from
cryosleep with hundreds of other personnel to work at the human colony on this inhabited Earth-sized
moon of Polyphemus, one of three fictional
gas giants orbiting
Alpha Centauri A.
Jake meets with Colonel Miles Quaritch (
Stephen Lang), a hardened and seasoned military veteran who is in charge of the colony. Quaritch welcomes the new personnel and soldiers and briefs them on Pandora. It is mostly covered with lush rainforests and wildlife, and home to the primitive Na’vi, a
sentient race of tall, blue-skinned,
cat-like
humanoids. The colony personnel and military are under the jurisdiction of the Resources Development Administration (RDA), a non-governmental organization back on Earth. Jake is introduced to Norm Spellman (
Joel David Moore), a
biologist who arrived on the same batch of personnel as he did, and Dr. Grace Augustine (
Sigourney Weaver), a
botanist as well as the leader of the Avatar program, which allows humans to control avatars, which are genetically engineered human-Na’vi
hybrids who look like Na’vis. A human's avatar contains DNA of that individual human; however, being identical twins, Jake can control Tom's avatar (that is the reason Jake was selected after Tom's death). While a human controls an avatar he is positioned in a kind of coffin in the lab, and his own body is asleep. During breaks, for example to report back and to eat, the avatar is at rest. Reasons for using avatars are that humans are unable to breathe Pandora's air, and bonding with Na’vi is easier with a similar body. In the case of Jake, an advantage is also that his own body being paralyzed is not a problem.
Using the avatars, Grace and her team have made some considerable progress teaching some Na’vi their ways and English as well as learning their language and culture. Grace is not pleased with RDA administrator Parker Selfridge’s (
Giovanni Ribisi) decision to use Jake to replace his brother’s avatar position, as she will have to spend time training him in Na’vi culture as well as teaching him how to control his avatar. Parker stresses that RDA needs to mine the extremely valuable mineral
unobtainium, which can be found in huge deposits on Pandora. Meanwhile, Quaritch makes Jake his informant to collect information on the Na’vi and their home, the Home Tree, which has huge deposits of unobtainium buried deep below its surface. He wants Jake to gain their trust and convince them to leave their home within three months.
After being trained for several weeks in his new body, Jake, Grace and Norm explore the native wildlife with Trudy Chacon (
Michelle Rodriguez), a retired Marine pilot who is assigned to ferry them to their location. While Grace and Norm study the wildlife, Jake encounters a group of Hammerhead Titanotheres, a rhinoceros-like animal species. However, the Titanotheres flee from a Thanator, a terrifying land predator. Grace shouts at her group to flee. Jake runs from the Thanator, who is after him, and loses his equipment and weapon in the process. He narrowly escapes death from the predator and falls into the raging rivers below.
As darkness falls, Jake creates a fire torch using a sap substance on the trees, and once more runs and fights a large group of small sized Viperwolfs. A female Na’vi named Neytiri (
Zoe Saldaña) rescues him and kills several of the Viperwolfs before they all flee. Neytiri is at first annoyed with Jake for having caused her to kill the Viperwolfs needlessly and leaves him. Jake goes after Neytiri, who tells him not to follow as she knows he is an avatar hybrid - a dreamwalker from the sky people. Jake is caught by her fellow Na’vi, but Neytiri defuses the situation by telling her people that she witnessed him being chosen by the seeds of Eyra, a spiritual entity that the Na’vi worship, which indicate him as a pure spirit.
Meeting Eytucan (
Wes Studi) and Mo’at (
C. C. H. Pounder), the king and queen of the Omaticaya tribe, who are also Neytiri’s parents, Jake presents himself as a warrior “dreamwalker”, a term the Na’vi used to call the avatar hybrids, with his intention to learn from them. Eytucan and Mo’at agree to teach Jake, making a reluctant Neytiri his tutor. From that day on, Jake spends his time learning the ways and culture of the Na’vi warriors, while jumping back to his original human body to report to Parker and Quaritch on information regarding the aliens. One day, Grace arranges for the Avatar team to be transferred to a remote camp on one of the floating islands to continue their program. Norm informs Jake that Grace knows and disapproves his regular communications with Quaritch, hence the team’s move.
In his avatar form, Jake learns how to bond and control his flying Banshee, while gaining respect and admiration from the Na’vi, his relationship with Neytiri continuing to grow, but also earning the jealousy and annoyance of Tsu’Tey (
Laz Alonso), Neytiri’s brother and next in line to be the clan leader. Reporting back to Quaritch, the colonel wants Jake to begin his plan to convince the tribe to leave the Home Tree, but Jake is now reluctant and weary of his fellow humans to exploit the moon’s resources. He tells Quaritch that he will attempt to convince the tribe once he is made part of the People, a ceremony granting the greatest honor to an avatar. That night, Jake undergoes the ceremony where Eytucan considers him as one of their own and made part of the People, with Grace and Neytiri looking on. While on a hunt, Jake and Neytiri encounter several
bulldozers, sent by RDA, destroying the nearby forests. In his attempt to stop them, Jake destroys one of the machine’s camera arrays. Returning to the Home Tree, Jake reveals he was sent by his superiors to convince the tribe to leave. He attempts to explain to the tribe that the humans will destroy them and their home if they don’t leave, but they are too upset by his apparent betrayal to listen. Neytiri refuses to listen to Jake’s explanations while Tsu’Tey attempts to kill him. Before anything else can happen, Jake and Grace are suddenly sent back to their human bodies when soldiers sent by Quaritch arrive and open their pods to take them back by force.
Quaritch and Parker have seen footage of Jake destroying the bulldozer’s cameras and have checked his entry logs, indicating him as losing interest to participate in the plan as well as committing possible treason. Grace tells an unbelieving Parker that the trees and plant life make up a huge network which connects the spiritual consciousness of all life, including the Na’vi, and must not be destroyed. Given a chance to attempt a final plea to the tribe to leave their home, Jake and Grace return to their avatar forms but are instead caught and bound by the Na’vi, who intend to defend themselves. A large strike force led by Quaritch destroys the Home Tree, burning it to the ground, while killing large numbers of the tribe, despite their attempts to retaliate. Mo’at releases Jake and Grace from their bonds and pleads them to save her tribe. Eytucan is killed in the destruction, leaving Neytiri devastated. She tells Jake to stay away when he tries to comfort her. In the chaos, Jake and Grace are sent back to their original bodies to be placed under arrest for treason, along with Norm, who tried to stop the military from disabling their avatar forms.
Trudy Chacon rescues the Avatar team from prison and flies them to safety, however Grace is shot by Quaritch when he attempts to stop them from leaving the colony. The team has the camp container holding the avatar transfer pods sent near the Tree of Souls, where the remaining Omaticaya tribe has fled to safety. Jake makes a plea to Mo’at to save Grace from dying by having her consciousness transferred permanently to her avatar form, using the Tree of Souls, before her human body expires. However, it is too late, as Grace is too weak to be transferred. Before she passes away, she tells Jake that she’s seen Eyra and the holy entity does exist. Later, Jake returns to his avatar form, which had been abandoned in the chaos. He makes his intention to redeem himself in the eyes of the Na’vi and successfully tames and controls a
Leonopteryx, a flying creature bigger than the Banshee, which a Na’vi has yet to accomplish in 4 generations, since Neytiri's grandfather's grandfather. Reaching the Tree of Souls, he asks Tsu’Tey, who has been made clan leader, and the entire tribe to stand with him and face the humans. Earning back the tribe’s trust, Jake makes plans to join forces with other clans to strike back at the human forces. Surveying the Na’vi, Quaritch learns that other clans have converged with the Omaticaya at the Tree of Souls and decides to destroy them and their holy ground to put an end to their defiance once and for all.
A huge military fleet commandeered by Quaritch approach the Tree of Souls, with the intention to blow the area up. Thousands of Na’vi warriors led by Jake and Tsu’Tey take to the skies and attack the fleet, causing huge losses on both sides. Neytiri is knocked off her Banshee and flees the military ground forces, while Norm’s avatar is shot and killed, forcing him to jump back to his original body. Tsu’Tey makes a valiant attempt to take down the shuttle carrying the explosives, but is killed in the process. Trudy goes against her fellow humans and attacks Quaritch’s ship which was attempting to shoot down Jake, but ends up having her ship shot down, killing her in the explosion.
When all things seem bleak, the native wildlife of Pandora strike back in force, which Jake earlier made a plea to Eyra for help. The ground and aerial troops are scattered by the wildlife and destroyed, while the shuttle carrying the explosives is destroyed before it reaches the Tree of Souls. Neytiri hitches a ride on a Thanator. Jake manages to bring down Quaritch’s ship, but the colonel manages to get into his AMP mech and escape the ship’s destruction. Finding the camp containing the avatar pods by chance, Quaritch attempts to destroy Jake’s body but Neytiri and her Thanator attack him. However, Quaritch kills the Thanator with his AMP and is about to kill Neytiri when Jake arrives to challenge him. After a short fight, Jake destroys the AMP’s life support but is caught in the mech’s grip. Neytiri saves Jake by planting two arrows into Quaritch’s chest, killing the colonel. The camp is damaged during Quaritch's attack and leaks oxygen, leaving Jake's human body almost dying from the poisonous air until Neytiri helps him put on his breath mask.
Having put an end to the military’s attack, the Na’vi round up the remaining humans to be sent back to Earth, never to return, while allowing a select group to stay with them on Pandora, which includes Jake, Norm and the avatar team. Jake decides to stay in his avatar form forever, and concludes his final entry log of his experiences. Returning to the Tree of Souls, he undergoes the consciousness transfer from his human body to his avatar form, and awakens to a new life as a Na’vi.
