Research scientist Galen Erso and his family are in hiding on the planet Lah'mu when Imperial weapons developer Orson Krennic arrives to press him into completing the Death Star, a space station-based superweapon capable of destroying entire planets. Galen's wife, Lyra, is killed in the confrontation while their daughter, Jyn, escapes and is rescued by rebel extremist Saw Gerrera.
Fifteen years later, cargo pilot Bodhi Rook defects from the Empire, taking a holographic message recorded by Galen to Gerrera on the desert moon Jedha. Rebel Alliance intelligence officer Cassian Andor learns of the Death Star from an informant and frees Jyn from an Imperial labor camp at Wobani. Cassian brings Jyn to the Rebel leader Mon Mothma, who convinces her to find and rescue Galen so the Alliance can learn more about the Death Star. Cassian is covertly ordered to kill Galen rather than extract him.
Jyn, Cassian, and reprogrammed Imperial droid K-2SO travel to Jedha, where the Empire is removing kyber crystals from the holy city to power the Death Star; Gerrera and his partisans are engaged in an armed insurgency against them. With the aid of blind spiritual warrior Chirrut Îmwe and his mercenary friend Baze Malbus, Jyn makes contact with Gerrera, who has been holding Rook captive. Gerrera shows her the message, in which Galen reveals he has secretly built a vulnerability into the Death Star and directs them to retrieve the schematics from an Imperial data bank on the planet Scarif.
On the Death Star, Krennic orders a low-powered test shot which destroys Jedha's capital. Jyn and her group take Rook and flee the moon, but Gerrera remains to die with the city. Grand Moff Tarkin congratulates Krennic before using Rook's defection and security leak as a pretext to take control of the project. Rook leads the group to Galen's Imperial research facility on the planet Eadu, where Cassian chooses not to kill Galen. Jyn makes her presence known moments before Rebel bombers attack the facility. Galen is mortally wounded by the bombers and dies in his daughter's arms, before she escapes with her group on board a stolen Imperial cargo shuttle. Krennic is summoned by Darth Vader to answer for the Death Star’s attack on Jedha City. Krennic seeks his support for an audience with the Emperor, but Vader instead Force-chokes him and orders him to ensure no further breaches occur.
Jyn proposes a plan to steal the Death Star schematics using the Rebel fleet but fails to gain approval from the Alliance Council, who feel victory against the Empire is now impossible. Frustrated at their inaction, Jyn's group lead a small squad of Rebel volunteers to raid the databank themselves. Arriving at Scarif (which is protected by a planet-wide shield) on the stolen Imperial ship, which Rook dubs "Rogue One", a disguised Jyn and Cassian enter the base with K-2SO while the other Rebels attack the Imperial garrison as a diversion. The Alliance learns of the raid from intercepted Imperial communications and deploys their fleet in support, revealing their full might to the Empire. K-2SO sacrifices himself so Jyn and Cassian can retrieve the data. Îmwe is killed after activating the master switch to allow communication with the Rebel fleet, and Malbus is killed in action shortly afterward. Rook is killed by a grenade after informing the Rebel fleet that it must deactivate the shield surrounding the planet to allow the transmission of the schematics. The Rebel commander, Admiral Raddus, uses a Hammerhead corvette to destroy two Star Destroyers, and the wreckage crashes atop the shield generator and punches a hole in the shield. Jyn and Cassian obtain the schematics, but they are ambushed by Krennic, who is eventually shot and wounded by Cassian. Jyn transmits the schematics to the Rebel command ship. The Death Star enters orbit above Scarif, where Tarkin uses another low-power shot to destroy the compromised base, killing Krennic, Cassian, and Jyn, along with all remaining ground Imperial and Rebel forces.
The Rebel fleet prepares to jump to hyperspace, but many of the fleet's ships are intercepted by Vader's arriving Star Destroyer. Vader boards the Rebel command ship and kills many of the rebel troops in an attempt to regain the schematics, but a small starship escapes with the plans on board. Aboard the fleeing ship, Princess Leia declares that the schematics will provide hope for the Rebellion.
Felicity Jones as Jyn Erso, a young renegade woman who is detained for her crimes against the Empire until she is freed by the Rebel Alliance. She has used many aliases during her life such as Lianna Hallik, Tanith Pontha, and Kestrel Dawn while her father affectionately calls her "Stardust".
Beau Gadsdon as 8-year-old Jyn
Dolly Gadsdon as 4-year-old Jyn
Diego Luna as Cassian Andor, a Rebel captain and intelligence officer.
Ben Mendelsohn as Orson Krennic, the director of advanced weapons research for the Imperial military.
Donnie Yen as Chirrut Îmwe, a blind warrior who believes in the Force. He is said to be one of the Guardians of the Whills.
Mads Mikkelsen as Galen Erso, Jyn's father and a research scientist.
Alan Tudyk as K-2SO, a former Imperial enforcer droid who was reprogrammed by Cassian Andor to serve the Rebellion
Riz Ahmed as Bodhi Rook, a former Imperial cargo pilot who defects to the rebels under the influence of Galen Erso.
Jiang Wen as Baze Malbus, a longtime companion of Chirrut Îmwe and one-time devoted Guardian of the Whills, now a Rebel warrior and mercenary.
Forest Whitaker as Saw Gerrera, a veteran of the Clone Wars and a friend of the Erso family who had mentored Jyn in her later childhood years.
Jimmy Smits, Genevieve O'Reilly, Anthony Daniels, and Jimmy Vee reprise their roles from previous films as Bail Organa, Mon Mothma, C-3PO, and R2-D2, respectively; Vee is uncredited for his role. James Earl Jones also reprises his role from previous films as the voice of Darth Vader, who is physically portrayed by Spencer Wilding during the meeting with Krennic and aboard the Star Destroyer, and by Daniel Naprous for the end scene. Grand Moff Tarkin and Princess Leia Organa are played by Guy Henry and Ingvild Deila, respectively, with the digital likenesses of Peter Cushing and Carrie Fisher superimposed. Henry also provides the voice for Tarkin, while archival audio of Fisher is used for Leia. Angus MacInnes and Drewe Henley are featured as Gold Leader Dutch Vander and Red Leader Garven Dreis, respectively, via unused footage from A New Hope; MacInnes returned to record new dialogue for Vander, while new dialogue for the deceased Henley was assembled from archival material. David Ankrum, who voiced Wedge Antilles in A New Hope, reprises his role in a vocal cameo. Ian McElhinney, Michael Smiley, Andy de la Tour, and Tim Beckmann play General Jan Dodonna, Dr. Evazan, General Hurst Romodi, and Captain Raymus Antilles, respectively. Warwick Davis plays Weeteef Cyubee, a member of Saw Gerrera's Partisans. Dave Filoni, known for his work on Star Wars: The Clone Wars and Star Wars Rebels, reprises his role from the latter series as C1-10P. Stephen Stanton, known for his numerous roles in The Clone Wars and Rebels, gives voice to Admiral Raddus, while Paul Kasey appears in costume as the alien character on-screen.
Additionally, Alistair Petrie plays General Davits Draven, Ben Daniels plays General Antoc Merrick, and Valene Kane plays Lyra Erso, Jyn's mother. Jonathan Aris, Fares Fares, and Sharon Duncan-Brewster appear as Senators Nower Jebel, Vasp Vaspar, and Tynnra Pamlo, respectively. Simon Farnaby plays a member of Blue Squadron. Jordan Stephens appears as Rebel Alliance member Corporal Tonc. Nick Kellington plays Bistan, the door gunner on a U-wing during the battle on Scarif. Ian Whyte plays Moroff, a member of Saw Gerrera's Partisans. Daniel Mays appears as Tivik. Rian Johnson and Ram Bergman, director and producer of Star Wars: The Last Jedi, respectively, cameo as two Death Star technicians.
It is the first installment of the Star Wars anthology series and an immediate prequel to Star Wars: Episode IV – A New Hope (1977).