Amid a galactic civil war, Rebel Alliance spies have stolen plans to the Death Star, a colossal space station built by the tyrannical Galactic Empire that is capable of destroying entire planets. Imperial Senator Leia Organa of Alderaan, secretly a Rebel leader, has obtained the schematics, but her ship is intercepted and boarded by an Imperial Star Destroyer under the command of the ruthless Darth Vader. Leia is taken prisoner, but the droids R2-D2 and C-3PO escape with the plans, crashing on the nearby planet of Tatooine.
The droids are captured by Jawa traders, who sell them to moisture farmers Owen and Beru Lars and their nephew, Luke Skywalker. While Luke is cleaning R2-D2, he discovers a recording of Leia requesting help from a former ally named Obi-Wan Kenobi. R2-D2 goes missing, and while searching for him, Luke is attacked by Sand People. He is rescued by Obi-Wan, an elderly hermit. Obi-Wan tells Luke about his past as one of the Jedi Knights, former peacekeepers of the Galactic Republic, who drew mystical abilities from "the Force" but were hunted to near-extinction by the Empire. Luke learns that his father, also a Jedi, fought alongside Obi-Wan during the Clone Wars until Vader, Obi-Wan's former pupil, turned to the dark side of the Force and murdered him. Obi-Wan offers Luke his father's old lightsaber, the signature weapon of the Jedi.
Luke, Leia and HanR2-D2 plays Leia's full message, in which she begs Obi-Wan to take the Death Star plans to Alderaan and give them to her father, a fellow veteran, for analysis. Luke initially declines Obi-Wan's offer to accompany him to Alderaan and learn the ways of the Force, but he is left with no choice after Imperial stormtroopers murder his family while searching for the droids. Seeking a way off the planet, Luke and Obi-Wan travel to the city of Mos Eisley and hire Han Solo, a smuggler indebted to local mobster Jabba the Hutt. Pursued by stormtroopers, Luke, Obi-Wan, R2-D2, and C-3PO flee Tatooine with Han and his Wookiee copilot, Chewbacca, on their ship, the Millennium Falcon.
Before the Falcon reaches Alderaan, the Death Star commander Grand Moff Tarkin has the planet obliterated by the station's gigantic laser. Upon arrival, the Falcon is captured by the Death Star's tractor beam, but the group escapes and infiltrates the station. As Obi-Wan leaves to disable the tractor beam, Luke persuades Han and Chewbacca to help him rescue Leia, who is scheduled for execution after refusing to reveal the location of the Rebel base. After disabling the tractor beam, Obi-Wan sacrifices himself in a lightsaber duel against Vader, which allows the rest of the group to escape the Death Star. Using a tracking device on the Falcon, the Empire locates the Rebel base on the moon Yavin 4.
Analysis of the captured Death Star schematics reveals a hidden weakness in a small exhaust port leading directly to the station's reactor. After collecting his reward for rescuing Leia, Han leaves the Rebels to pay off Jabba. Luke joins the Rebels' X-wing squadron in a desperate attack against the approaching Death Star. In the ensuing battle, Vader leads a squadron of TIE fighters against the Rebels, and they suffer heavy losses. Han and Chewbacca unexpectedly return to aid them in the Falcon, knocking Vader's ship off course before he can shoot Luke down. Guided by the voice of Obi-Wan's spirit, Luke uses the Force to aim his torpedoes down the exhaust port, causing the Death Star to explode moments before it can fire on the Rebel base. In a triumphant ceremony, Leia awards Luke and Han medals for their heroism.
