Jacob Sully is a former 22 year old paraplegic Marine veteran at the start of the first film. Jake becomes one of the 20 known avatar drivers and later becomes a renegade after defecting to the Na'vi species after witnessing the RDA's greed and brutality against the Na'vi during the destruction of the Hometree.

After his twin brother, Tom, was murdered on Earth, Jake replaced him in the Avatar Program on Pandora, in which humans remotely control human/Na'vi hybrids to safely navigate the planet. He was originally assigned to gather intel that would help Colonel Quaritch find a way to force the Na'vi to leave Hometree, or destroy it if necessary, as the Na'vi occupation of Hometree was blocking the RDA's access to a very large deposit of unobtanium underneath the tree. After spending time with the Na'vi, Jake abandons his original mission and stops reporting to Quaritch. Jake learns the ways of the Na'vi hunters from Neytiri and falls in love with her. He is eventually accepted into the Omatikaya clan and becomes Neytiri's mate. He turns against the RDA and, after becoming the sixth Toruk Makto, leads the Na'vi in a battle to drive the RDA off Pandora.

After driving off the humans, he lives a life on Pandora and guides the clan as a clan leader. Jake and Neytiri become the parents of three biological children (Neteyam, Lo'ak and Tuktirey), as well as an adoptive daughter Kiri. However, the RDA would return, causing Jake and the Omatikaya clan to flee, entering a war, but when Quaritch returned as a Recom, Jake and his family left the clan to take refuge with the Metkayina clan, learning their ways. Due to the kidnapping of their children, Jake and Neytiri fought side by side with the Metkayina against the RDA, eventually joining the Metkayina clan.

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  PERSONALITY:    Little is shown of Jake's life on Earth, however, he seems to have a real gloom and pessimistic view of the world. He describes it as “the strong always wanting to prey on the weak”,  which implies he may have gone through some hardships during his lifetime. 

Jake is the “brawn” to Tom’s “brain”. He thrives off adventure and has a strong desire to feel free, having enjoyed mythological stories of heroes with his brother when he was young. Jake also greatly enjoys being challenged and pushing himself to his limits; he once tried to convince himself that he could pass any test a man can pass. He became a Marine for the tough and challenging lifestyle and "be hammered on the anvil of life" as he calls it.

At first, he seems callous and sarcastically indifferent, potentially as a way for him to cope with many of his stressful unfortunate life experiences. However, as he becomes familiar with someone, he begins to trust and respect them, taking his relationships very seriously.

He can be rash, impulsive and clumsy. He is shown being easily distracted sometimes, resulting in him disobeying orders. Jake's youthful nature does have some flaws, however; while he is shown to be courageous, determined, passionate, and possesses exceptional strength of character, this is sometimes to the fault of dangerous recklessness. He has also been accused of being arrogant. Sometimes, it takes him a while to finally listen to other people.

Two weeks following the war, Jake's mental health turns for the worse as he begins to struggle with his festering dark emotions and guilt, due to the lives lost throughout the war. He is shown to have become more distant from Neytiri, spending more time alone in the forest viewing the remains of his former human body, and becomes uncertain about his future. Guilt-ridden and tormented, he becomes very reckless about his own life, seen when he is willing to engage in a battle to the death with Arvok, suggesting he may have survivor's guilt. While in his near-death experience coma, he is seen facing his own regrets, tormenting himself over the possibility that if he had only spoke up to the Na'vi more about RDA's intentions sooner, then he could have potentially saved many human and Na'vi lives such as Trudy, Grace, Eytukan and Tsu'tey. He grows fears over whether or not his existence will continue to bring pain, suffering and death onto others. After he hears from Eytukan that he is not beyond redemption, that he ultimately never intended to hurt anyone, that he does not deserve to die, and that he must learn how to forgive himself, Jake is able to begin his own path of self-healing from his traumatic experiences.