On the planet Lah'mu, research scientist Galen Erso is forcibly recruited by Imperial weapons developer Orson Krennic to complete the design for the Death Star, a space station capable of destroying entire planets. Galen's wife, Lyra, is killed in the ensuing confrontation while their daughter, Jyn, escapes and is taken in by Rebel extremist Saw Gerrera.
Several years later, Imperial pilot Bodhi Rook defects from the Empire, taking a holographic recording of Galen to Gerrera on the moon Jedha. Jyn, now an adult, is freed from Imperial captivity by Rebel intelligence officer Cassian Andor and convinced to rescue Galen so they can learn more about the Death Star. However, Cassian is covertly ordered to kill Galen rather than extract him. Jyn, Cassian, and reprogrammed Imperial droid K-2SO travel to Jedha in the midst of an armed uprising against the Empire. With the help of blind warrior Chirrut Îmwe and mercenary Baze Malbus, Jyn reunites with Gerrera, who is holding Rook captive. Gerrera shows Jyn her father's recording, where Galen reveals that he has secretly constructed a vulnerability in the Death Star's reactor that can be exploited by the Rebellion, and directs them to retrieve the structural plans at an Imperial data bank on the planet Scarif.
Aboard the Death Star, Krennic orders the capital of Jedha destroyed as a demonstration of the space station's power; while Jyn and the rest of the group escape to safety, Gerrera remains to die in the city. Grand Moff Wilhuff Tarkin congratulates Krennic before using Rook's defection and a security leak under Krennic's command as a pretext to take control of the project. Meanwhile, Rook leads the group to Galen's research facility on the planet Eadu, where Cassian chooses to spare Galen's life. Shortly afterwards, Rebel forces attack the facility, leaving Galen fatally injured. Jyn and the rest of the group manage to escape aboard a stolen Imperial cargo shuttle. Meanwhile, Krennic meets Darth Vader, seeking his support and an audience with the Emperor, but Vader declines.
Jyn proposes a plan to the Rebel leadership to steal the Death Star plans on Scarif, but the Rebel leadership declines, feeling that victory against the Empire is now impossible. Nevertheless, Jyn's group, along with a number of Rebel volunteers, set off to Scarif to raid the data bank. While the Rebel forces battle the Imperial garrison stationed on the planet, Jyn, Cassian and K-2SO search the data banks for the Death Star plans. The Rebel fleet, learning of the raid, arrive in support. In the ensuing battle, most of Jyn's group are killed, leaving only Jyn and Cassian alive. They manage to retrieve the Death Star plans and transmits it to the Rebel fleet, but Krennic ambushes the two, wounding Cassian and pursuing Jyn to a roof, cornering her. Before he can kill her, however, Cassian shoots and injures Krennic. The Death Star enters orbit above Scarif and, on orders from Tarkin, destroys the base, killing Jyn, Cassian and Krennic.
The Rebel fleet attempts to jump into hyperspace, but are intercepted by Imperial forces led by Darth Vader, who boards the Rebel command ship and attempts to retrieve the Death Star plans. However, Rebel forces manage to narrowly escape the massacre with the Death Star plans. Aboard the fleeing ship, Princess Leia declares that the Death Star plans will provide hope for the Rebellion.