In Star Wars Episode IV: A New Hope, Leia is introduced as he Princess of Alderaan and a member of the Imperial Senate. Darth Vader captures her onboard the ship Tantive IV, where she is acting as a spy for the Rebel Alliance. He accuses her of being a traitor and demands to know the location of the secret technical plans of the Death Star, the Galactic Empire's newest and most powerful weapon. Unknown to Vader, the young senator has hidden the plans inside the Astromech droid R2-D2 and has sent it to find Jedi Master Obi-Wan Kenobi on the nearby planet of Tatooine. Later, Vader has her tortured, but she resists telling him anything. Still believing she could be useful, the Death Star's commander, Grand Moff Tarkin, threatens to destroy Alderaan with the superweapon unless she reveals the location of the hidden Rebel base. She lies to them, and Tarkin orders Alderaan to be destroyed anyway.
She is finally rescued by Luke Skywalker, Obi-Wan Kenobi, Han Solo, the Wookiee Chewbacca, and the two droids, R2-D2 and C-3PO. When they finally escape, at the expense of Obi-Wan's life (sacrificed in a duel with Vader), they take part in the Battle of Yavin, in which Luke destroys the Death Star in his X-wing fighter. In the Massassi Temple at the hidden Rebel base on Yavin 4, the radiant Princess Leia Organa presents the Alderaanian Medal of Freedom to her rescuers and the heroes of the battle.
In Star Wars Episode V: The Empire Strikes Back -set three years later- Leia is at the Rebel base on Hoth. She later helps with the evacuation of Hoth during an Imperial attack, remaining at her station until Han forces her to leave with him. She flees with C-3PO, Han, and Chewbacca on Han's ship, the Millennium Falcon. Although they are pursued by Imperial TIE fighters, they dodge their fire by flying into an asteroid field when the Falcon's hyperdrive breaks down. Romance blossoms between Leia and Han during their flight from the Empire; while hiding in the stomach of a space slug, she finally shares a kiss with the Corellian smuggler. Later, when they stop at Bespin for repairs, Han's friend Lando Calrissian turns them over to Vader, who uses them as bait for Luke. Han is also used as a test subject for the carbon freezing chamber meant for Luke, and it is there that Leia finally confesses her love for Han. Vader then gives the frozen Han to bounty hunter Boba Fett to give to Jabba the Hutt, to whom Han owes a very large debt. Later, Lando helps Leia, Chewbacca, and the two droids escape. While escaping, she senses that Luke is in trouble and makes them go back for him. They save Luke, who is badly hurt after a near-fatal duel against Vader.
In Return of the Jedi, set a year later, Leia, Chewbacca, Lando, Luke (now nearly a Jedi Knight), and the droids go to Tatooine to try to rescue Han Solo from Jabba the Hutt. Leia's part of the plan consists of posing as the Ubese bounty hunter Boushh, who will turn Chewbacca over to Jabba. Her ruthless bargaining, negotiating the price for Chewbacca at the end of a thermal detonator, impresses Jabba enough to allow her quarters in the palace for the night. The Huttese gangster eventually discovers her real identity, captures her, makes her his new slave girl.
After Luke kills the Rancor, Jabba sentences Luke and Han to be fed to the Sarlacc. Just as all seems lost, Lando, disguised as a guard, helps Luke and Han overpower their captors. Leia seizes the moment to kill Jabba by strangling him with the very chain that bound her. R2-D2 cuts her loose, and after Luke boards the sailbarge, he rescues Leia. With Leia's help, Luke uses a deck cannon to blow up his barge as they swing to safety.
While preparing for a last battle with the Empire on Endor, Luke reveals to a stunned Leia that she is, in fact, his twin sister, and that Vader is their father. Initially reluctant to believe him, Leia realizes that Luke speaks the truth and joins Han Solo in leading the Rebels in battle on Endor as the Rebel Fleet battle the second Death Star. Leia is slightly injured in the battle, but nevertheless helps the Rebels, allied with the Ewoks, to defeat the Empire.