Gamora was a former Zehoberei assassin and a former member of the Guardians of the Galaxy. She became the adopted daughter of Thanos and adopted sister of Nebula after he killed half of her race.
Gamora served him for years before betraying him in an attempt to free herself from his ways. She was hired to steal the Orb, and after becoming involved in the Quest for the Orb, she befriended the other members of the Guardians of the Galaxy.
After the Battle of Xandar, she left to work with them all. Having made a deal with the Sovereign to kill the Abilisk, Gamora was able to regain custody of Nebula with the intention of finally bringing her to justice in Xandar.
However, her mission to punish Nebula was delayed when Gamora and the Guardians came into contact with Ego, the long-lost father of Star-Lord. While Ego claimed he simply wanted to bond with his son, Gamora was suspicious and, alongside Nebula who had freed herself, discovered Ego's evil intentions to destroy and rebuild the universe.
Upon this discovery, the Guardians teamed up to destroy the living planet, succeeding with the help of Mantis, who joined the group, but at the cost of Yondu Udonta sacrificing his life. After Udonta's death, Gamora finally confessed that she had romantic feelings for Star-Lord and started a relationship with him.
Four years later, Gamora and the Guardians intercepted a distress call sent by Asgardians; Thor warned them that Thanos had begun searching for the Infinity Stones himself.
Realizing what Thanos intended to do with them, Gamora led her friends to Knowhere to procure the Aether, only for both it and Gamora to be captured by Thanos himself. Thanos took Gamora to Vormir, where he sacrificed her against her will in order to obtain the Soul Stone, a process that trapped Gamora's soul inside the Soulworld.
In 2023, the Time Heist orchestrated by the Avengers with the intention of undoing the Snap inadvertently enabled the 2014 versions of Gamora and Thanos to learn how the future would unfold, causing a major divergence from the established timeline.
Acting upon the obtained intelligence, Thanos successfully brought his armies from 2014 to the future where Gamora eventually turned against him after learning her tragic future before helping the Avengers and their allies to defeat him once and for all.
After surviving the battle, Gamora fled, with Quill and the other Guardians beginning their search for her.