Four years after the end of the Clone Wars and the establishing of the Galactic Empire, former Imperial research scientist Galen Erso is approached by his superior, Director Orson Krennic, who requests his return because "the project" they were working on has stalled. Erso initially refuses, but when Krennic refuses to take no for an answer, Galen's wife Lyra is killed in the ensuing confrontation and he is taken into Imperial custody. Their daughter Jyn, told to hide by her parents before Krennic's arrival, is rescued by Saw Gerrera, a member of the Rebel Alliance and old friend of the Erso family.
Fifteen years later, Jyn Erso is a young woman living under an assumed name, and currently incarcerated at an Imperial labour camp on the planet Wobani when she is broken out of captivity by Rebel Alliance commandoes. Concurrently, Cassian Andor, a captain in the Alliance, learns from an informant that an Imperial defector on the planet Jedha is claiming the Empire is building a weapon with the power to destroy entire planets. On Yavin IV, home base of the Rebel Alliance, Jyn is informed that the Imperial defector on Jedha is claiming to have been sent by her father, who is reportedly the top scientist working on this weapon. The defector is being held by Saw Gerrera's militants on Jedha; since the Alliance expelled Saw and his men several years ago for their extremism, the Alliance hopes sending Jyn to Saw, given their past connection, will convince Saw to let the Alliance corroborate his prisoner's testimony. Should it prove genuine, the Alliance intends to recover her father from Imperial custody and have him testify before the Senate as to the Emperor's plans for this weapon, as well as providing Jyn a new identity and enough funds to start a new life elsewhere. Jyn is despatched to Jedha with Cassian and K2-SO, a reprogrammed Imperial security droid, though before their departure, Cassian is ordered by his superior, General Draven, to kill Galen rather than rescue him.
On Jedha, Cassian explains that the Imperials are strip-mining the planet for kyber crystals, the same material once used by the Jedi to power their lightsabers, as fuel for the weapon. With the aid of two locals of the planet's capital, Chirrut Îmwe and Baze Malbus, Jyn and Cassian assist Saw's partisans in a skirmish against Jedha's Imperial garrison and are brought to Saw's headquarters. While Cassian, Chirrut and Baze are imprisoned with the defector, a pilot called Bodhi Rook, Saw shows Jyn the message Bodhi claims to have brought from her father. In it, Galen explains that what he has helped build is a moon-sized space station called the "Death Star", armed with firepower sufficient to destroy a planet. Galen also explains that he built a hidden weakness into the Death Star that, if exploited, will cause the destruction of the entire station. The weakness, Galen explains, can be found in the Death Star's schematics, currently housed in a data vault in an Imperial facility on the planet Scarif.
Concurrently, Krennic is reprimanded by his direct superior, Grand Moff Tarkin, as Bodhi's defection is a security leak risking the Death Star's exposure to the galaxy at large ahead of schedule, so Krennic grudgingly orders a test firing of the Death Star on Jedha to eliminate any potential witnesses to its existence. The shot destroys Jedha's capital and causes a shockwave that decimates the surrounding area; Jyn, Cassian, Bodhi, Chirrut, Baze and K2-SO escape in the nick of time, though Saw chooses to stay behind to die. In the aftermath of the test firing, Tarkin uses the security leak to justify taking control of the Death Star; when Krennic protests, Tarkin retorts that Bodhi was dispatched from Galen Erso's research facility on Eadu, implying the security breach goes even higher.
Bodhi informs Jyn and her companions of Galen's location on Eadu, and she convinces Cassian to head there to rescue her father so he can personally confirm the Death Star's existence to the Rebel Alliance. Upon reaching Eadu, their ship is shot down by Imperial anti-air defences, and Cassian goes to scout ahead, in truth to seek out a position to snipe Galen. Jyn follows discretely, while Krennic arrives to reprimand Galen for leaking intel on the Death Star to the Rebel Alliance. Though Cassian can't bring himself to fire a killing shot, Rebel starfighters dispatched by Draven as reinforcements arrive and begin bombing the facility; Galen is fatally injured in the crossfire, dying in his daughter's arms. The group escape Eadu aboard a stolen Imperial cargo shuttle and retreat to Yavin IV, whereupon Jyn and Cassian angrily confront each other; her accusing him of being willing to murder her father in cold blood, him retorting that she doesn't get to judge his methods when she only became invested in the rebel cause because she developed a personal stake in the conflict.
Krennic journeys to Mustafar to petition Darth Vader into arranging an audience with the Emperor to impress upon the latter Krennic's right to command the battle station; Vader reprimands Krennic for his presumption and angrily orders him to ensure Galen has not potentially sabotaged the Death Star further. On Yavin, the Alliance argues over their best course of action; some disbelieve the Death Star even exists, while others fear the potential it does makes the Empire unassailable. Jyn proposes launching a raid against the Imperial data archive on Scarif, acquire the Death Star plans and exploit the weakness the plans contain, but despite support from much of the Alliance military's top brass, the Alliance's political wing deems it too risky and declines. Afterwards, Jyn is approached by Cassian, who has rounded up several dozen Alliance fighters; Cassian believes that if the Alliance submits to the Empire for fear of the Death Star, everything he and those with him have done has been for nothing. Jyn, along with Cassian, his reinforcements, Baze, Chirrut, Bodhi and K2-SO depart for Scarif aboard the captured Imperial shuttle, under the call sign "Rogue One". Concurrently, Senators Mon Mothma and Bail Organa conclude further conflict with the Empire is inevitable, the former urging the latter to contact "the Jedi" for help, with Organa agreeing to send his most trusted agent to do so.
Bodhi's Imperial clearance allows Rogue One to infiltrate Scarif, given the planet is swathed in a colossal shield only accessible through an Imperial controlled gate; Krennic also arrives concurrently, intending to examine the data archives to see whatever sabotage Galen may have inflicted. Once planet-side, Jyn, Cassian and K2-S0 infiltrate the bases while the remaining commandos lay explosives around the perimeter; when the base's security proves too tight for Jyn's group to infiltrate further, the commandos detonate the explosives at Cassian's signal. Krennic panics and orders Scarif's Imperial garrison to deal with the incursion, and the reduction of stormtroopers inside the base allows Jyn, Cassian and K2-S0 to reach the data archive as battle erupts between the Rebels and Imperials outside. The Rebel Alliance and the Empire quickly learn what is going on; the Alliance scrambles its fleet to reinforce the infiltrators, while Tarkin orders the Death Star jump to hyperspace bound for Scarif, as well as ordering Darth Vader to meet them en route.
Jyn, Cassian and K2 are able to reach the data archive. While K2 holds off the stormtroopers trying to defend the archive, Jyn and Cassian acquire the plans. The Rebel fleet arrives at Scarif, and the Imperials seal the planetary shield, though not before several Rebel ships make it through to reinforce those fighting planetside. Before being overwhelmed, K2 informs Jyn and Cassian that if the shield can be brought down, they can broadcast the plans directly to the Rebel fleet using the facility's own satellite dish. At the same time, Krennic is informed of Jyn and Cassian in the archive and takes his personal guard to deal with the problem, and Cassian is seemingly gunned down helping Jyn escape.
As the battle outside turns against the Rebels, Bodhi, Chirrut and Baze, at the cost of their own lives, are able to get a message to Admiral Raddus, commander of the Rebel fleet, informing him the shield has to be disabled for them to transmit the plans. Jyn reaches the facility's summit, only to be held at gunpoint by Krennic. As he brags that the Rebels' plans to exploit the weakness her father hid inside the Death Star will fail, a wounded but alive Cassian incapacitates Krennic. Concurrently, Admiral Raddus has the Alliance fleet crash a crippled Imperial Star Destroyer into the space station generating the planetary shield, allowing Jyn to upload the plans to Admiral Raddus's flagship, the Profundity just as the Death Star emerges from hyperspace.
As Jyn and Cassian, the last survivors of Rogue One's crew flee the Scarif base, Tarkin orders the Death Star to fire on the base, destroying it (along with Krennic). With no hope of escape, Cassian and Jyn simply wait on a nearby beach, Cassian telling Jyn her father would be proud of her and both embracing as the blast wave from the Death Star's superlaser reaches them. With the plans secure, the Rebel fleet scatters in all directions just as Darth Vader's personal Star Destroyer, Devestator emerges from hyperspace. The Devestator cripples the Profundity and Vader personally leads a boarding party to recover the Death Star plans; unfortunately, despite his best efforts, the Profundity's crew are able to abandon ship by the skin of their teeth, fleeing aboard the Tantive IV while Vader can only helplessly watch them escape.
Aboard the Tantive IV, a Rebel soldier hands the plans to Princess Leia Organa, who remarks the plans will offer hope in the struggle to come.
