The opening crawl reveals that Han Solo's friends are engaged in a mission to rescue the smuggler from Jabba the Hutt and that the Galactic Empire is building a new armored space station which is even larger and more powerful than the first Death Star.
Near the forest moon of Endor the new Death Star is being constructed in orbit, and a command star destroyer arrives and launches a shuttle with a fighter escort -- a shuttle bearing the Dark Lord of the Sith. Fearing his arrival, the commander of the new Death Star informs Darth Vader (David Prowse
, voice: James Earl Jones
) that the station will be operational on schedule, but when Vader challenges this optimistic appraisal of the situation, the commander admits that he needs more men to accelerate construction. Darth Vader, however, informs the commander that the Emperor (Ian McDiarmid
) will be arriving soon, and that he is most displeased with the commander's progress. Shaken, the commander commits to redoubling construction efforts. Vader, pleased, remarks, "the Emperor is not as forgiving as I am."
Jedi Knight Luke Skywalker (Mark Hamill
), Chewbacca (Peter Mayhew
), Lando Calrissian (Billy Dee Williams
), Princess Leia Organa (Carrie Fisher
), C-3PO (Anthony Daniels
), and R2-D2 (Kenny Baker
) return to Tatooine to rescue Han Solo (who was encased in carbonite at the end of Star Wars: Episode V - The Empire Strikes Back
) from the gangster Jabba the Hutt (voice: Larry Ward
). Luke sends C-3PO and R2-D2 to Jabba's desert palace to deliver a message: In a hologram projected by R2, Luke offers to bargain with Jabba for Solo himself. Jabba laughs at the message, saying he refuses to give up his "favorite decoration": Han, frozen in carbonite, hangs on a wall in Jabba's court.
Disguised as a bounty hunter named Boushh, Leia arrives in Jabba's court with Chewbacca in cuffs. She offers him to Jabba for a sizable bounty. After Leia dickers with Jabba over the amount and threatens him with a small thermal detonator, Jabba happily agrees and Chewbacca is imprisoned.
That night, Leia sneaks into Jabba's court and frees Han from the carbonite. However, she and Solo are both captured by Jabba. Solo is imprisoned with Chewbacca and Jabba keeps Leia on display in a metal bikini. Luke arrives with a final ultimatum to release Solo. Jabba again refuses and drops Luke through a trap door into a pit below his throne that houses the rancor, a fearsome beast that Jabba keeps for executions. Luke defeats the rancor, enraging Jabba, who declares that Luke, Solo and Chewbacca will be slowly consumed by the sarlacc (a huge, shark-toothed, tentacled maw at the bottom of the Great Pit of Carkoon). With the help of the Force and R2-D2, Luke escapes and arms himself with a new lightsaber. A battle erupts, with Luke steadily taking the fight to Jabba's men. During the battle, Leia strangles Jabba and with R2-D2's help escapes from her bonds, and Solo accidentally knocks Boba Fett (Jeremy Bulloch
) into the sarlacc pit. Luke, having fought his way onto Jabba's sail barge, has the escaping Leia aim the deck cannon at the vehicle and sets it on automatic fire; the sail barge soon blows apart. Our heroes manage to escape before it explodes. Luke flies off Tatooine in his X-Wing fighter and the rest of the band fly away in the Millennium Falcon to rendezvous with the Rebel fleet near Sullust.
A massive fleet of fighters completely surrounds the boarding bays of the Death Star at the arrival of the Emperor. As Red Guards slowly descend from the Imperial Shuttle and flank its ramp, Vader and the Death Star commander kneel to their master, the last to enter the hangar. He insists that Lord Vader will soon capture Luke Skywalker, and Luke will learn of the dark side of the Force.
Luke returns to Dagobah to complete his Jedi training, but he finds Yoda (voice: Frank Oz
) is ill. He tells Luke that no further training is required and all that remains to be done is to confront Darth Vader. Luke attempts to get independent confirmation of Darth Vader's claim to be Luke's father, but Yoda is evasive. Finally, Luke begs Yoda to tell him the truth, and Yoda, emotional torture clearly evident on his normally serene features, confirms Luke's darkest fears. He correctly infers that Vader has used this information as an emotional weapon against Luke, and criticizes Luke for having faced Vader prematurely, with nearly disastrous consequences. He reminds Luke of the true nature of the Force, and of the soul corrupting nature of the dark side. Yoda then issues a dark warning, telling Luke how his father fell to the shadow: He was corrupted by the powers and influence of the Emperor. If Luke allows himself to be manipulated by this dark mind, then he, too, shall become what he most fears.
Finally, Yoda charges Luke with keeping alive the teachings and knowledge of the Jedi, urging him to start with his own family, with whom the Force is unnaturally strong. With his final breath, Yoda tells Luke that there is another Skywalker. Yoda dies at peace, and before Luke's astonished eyes, his body vanishes, passing with his spirit into the Force. The spirit of Obi-Wan Kenobi (Alec Guinness
) confronts a distraught Luke, confirming that Vader was once Anakin Skywalker, a Jedi who was turned to the dark side of the Force. Obi-Wan confesses to Luke that he made mistakes in Anakin's training, especially by not deferring to Yoda, and takes responsibility for indirectly creating the evil Darth Vader. Luke counters that even now, all is not lost, that some part of Anakin remains, if only someone can reach it. It is also revealed that the other Skywalker is Luke's twin sister, hidden from Anakin under an anonymous identity, and separated from Luke at birth to protect them both from the Emperor. Luke intuits that his sister is Princess Leia. Obi-Wan confirms it, but warns Luke that in the eyes of the Empire, all bonds of love and caring are potential weaknesses to be exploited.
Meanwhile, the entire Rebel Alliance is meeting to devise an attack strategy. As part of the attack, Luke and his companions (whom he rejoins after leaving Dagobah) must land on the forest moon of Endor and deactivate the generator that projects a protective shield up to the orbiting and incomplete Death Star. The team, led by Han, will use a stolen Imperial shuttle and confirmation code to infiltrate the heavy security measures protecting the construction site. The team makes it past the Imperial ships patrolling the site and lands on the moon.
When they arrive on the moon, the team happens across a small unit of Imperial biker scouts. Han tries to sneak up on the scouts to disarm them but is unsuccessful. Leia and Luke jump on speeder bikes and pursue two more scouts through the forest at high speed. They overtake them both but are separated; Leia's bike crashes into a tree after she jumps off and she falls unconscious. Luke jumps off his own bike and battles with the the scout he'd been pursuing, forcing him to crash using his lightsaber. When Luke rejoins the team, he finds that Leia hasn't returned. The team looks for her but is captured by local creatures called Ewoks -- short, furry, intelligent forest dwellers. An Ewok called Wicket (Warwick Davis
) befriends Leia, but the other Ewoks who captured the rest of the Rebel party decide to sacrifice them to C-3P0, who they believe is a god. Luke, having mastered the Force, levitates C-3P0 to impress the Ewoks with the droid's power and scare them into giving up the sacrifice. With the help of C-3PO, Luke and his party form an alliance with the Ewoks, whose stone-age technology has unexpectedly effective military applications.
Later, Luke decides that the time has come for him to face Vader. He confesses to Leia that he is her brother, and that he has to try to save the man who was once their father. He surrenders peacefully to Vader but fails to convince his father to abandon the dark side.
They go to the Death Star to meet the Emperor, who reveals that the Rebel Alliance is walking into a trap. On the forest moon, the Rebels led by Solo and Leia enter the shield generator control facility only to be taken prisoner by waiting Imperial forces. Once they are led out of the bunker, however, the Ewoks spring a surprise counterattack. In a desperate ground battle, the Rebels and Ewoks fight the Imperial forces. Aboard the Death Star, the Emperor attempts to seduce Luke with the powers of the dark side. The Emperor reveals his plan: the information that Rebel spies had stolen was part of an elaborate plan to draw out the Rebel fleet and command so they could be eliminated in one battle. As Luke's anger builds he attacks the Emperor with his lightsaber, only to be stopped by the crimson blade of Vader's lightsaber.
During the strike team's assault, the Rebel fleet emerges from hyperspace for the battle over Endor, only to discover that the shield of the Death Star is still functioning. An intense space battle takes place as the Rebel fleet battles to give the surface party more time to deactivate the Death Star's shield. During the battle, the Death Star is revealed to be operational; its superlaser is fired at the Rebel fleet and obliterates a Rebel star cruiser.
On the Death Star, the Emperor tempts Luke to give in to his anger. A ferocious lightsaber duel has erupted between Luke and his father. In the midst of combat, Vader reads Luke's feelings and learns that Luke has a twin sister. When Vader toys with the notion of turning Leia to the dark side, Luke gives in to his anger and gains the upper hand in the battle, slicing off Vader's right robotic hand in a rage in one swift cut, and makes his father succumb to defeat at the mercy of his son's blade. Despite the Emperor's goading Luke refuses to kill his father, realizing that he is traveling down his father's path towards the dark side, and declares himself a Jedi. Realizing that Luke cannot be turned, the Emperor uses Force lightning against him to torture and attempt to kill him. Deeply affected by the sight of his son dying before him, Vader repents and turns on the Emperor, throwing him down a reactor shaft to his death. At the same time, however, the Emperor's Force lightning causes fatal injuries to Vader (Anakin) and short-circuits his breathing system. Knowing that there is no hope for his own survival, Anakin asks Luke to take his mask off. Luke removes the helmet, revealing the pale and scarred face of his father. Anakin says that Luke was right about him, and asks Luke to tell his sister. With those final words, Anakin dies.
Back on Endor, the strike team finally destroys the shield generator. The Rebel fleet seizes the opportunity to launch a final assault on the Death Star in space. Lando leads Wedge Antilles (Denis Lawson
) and his fighter group into the bowels of the Death Star, where they fire at the main reactor, causing its collapse. Luke, with the body and armor of Anakin, escapes the Death Star in an Imperial shuttle. Moments later, Wedge in his X-Wing and Lando in the Millennium Falcon emerge from the Death Star just as the space station explodes. On Endor, Leia reassures Han Solo of her love and reveals to him that Luke is actually her brother. That evening, Luke cremates the remains of his father in a funeral pyre on Endor. The entire galaxy celebrates the fall of the Emperor and the Rebel victory over the Empire. Luke, Leia, Han, Lando, and the rest of the rebels, along with the Ewoks, celebrate the victory as well. During the celebration, Luke catches sight of the spirit figures of Obi-Wan Kenobi, Yoda, and the redeemed Anakin Skywalker, who look proudly upon him.