- Sam Worthington as Green Lantern/Hal Jordan
- Javier Bardem as Atrocitus
- Josh Brolin as Amon Sur
- Ed Harris as Abin Sur
- Anne Hathaway as Carol Ferris
- Stanley Tucci as Thaal Sinestro
- Dennis Haysbert as Kilowog
- Stellan Skarsgard as Tomar-Re
- Charlie Day as Tom Kalmaku
- Anthony Hopkins as Ganthet
- Tricia Helfer as Boodikka
- Alexander Ludwig as Jack T. Chance
- Nathan Lane voices Zox
- as Bleez
- Tom Kenny voices Qull
All the Guardians beside Ganthet don't speak.
Opening Credits: An unspecified voice tells of the origins of the Guardians of the Universe, and their original task force, the Manhunter robots. These Manhunters went beserk, and destroyed an entire sector. The Guardians then created a new squad of protectors, the Green Lanterns, who were living beigs that used rings powered by will. The first task of these Lanterns was the bring down the 5 survivors: Atrocitus, Dex, Qull, Bleez, and Zilius Zox. They had gone on a rampage and enslaved thousands of worlds by killing their leaders, and starting a harsh dictatorship. The Lanterns managed to track the five to Shard, a base made from renmants of Atrocitus' world. After a long battle, the five were defeated. The Lanterns destroyed the base on Shard, and crucified the five to the ground. Shard was thousands of miles from any planet, and so the five were left floating there, helpless because no one knew of their whereabouts.
As a child, Hal Jordan loved to watch his dad fly planes. One day, when he (and a couple hundred other people) was watching his dad test out a new plane, his dad crashed. The plane burnt up, his father was incinerated, and plane debris scattered everywhere. Some of it hit Hal, who got severely burned. His mom rushed him to a hospital, and when they were there she forbid him from ever flying a plane, looking at one, or doing anything related to them ever again.He disobeys her, and when he becomes 18, he becomes a test pilot for Ferris Air. His mom vows never to speak to him again unless he quits. He doesn't, and stays with his job for 11 years. Then, on the day when he is supposed to exhibit a new plane for a senator, he gets a call saying that his mom had a heart attack. When he is supposed to fly the plane, he purposely crashes it, so that they will fire him. They do, and he drives to the hospital to see his mom.
Unfortunately, she has already died by the time he reaches the hospital. Hal feels really depressed/guilty about this, and isn't paying attention when he drives home. He accidentally drives off the side of a bridge, but just before he hits water, he is pulled out of his car in a floating green bubble. The bubble lands near a dying alien named Abin Sur, who tells Hal that he is Sur's successor as a Green Lantern. Hal tries to call for help, but no one is nearby. He tells Sur that he does't know what a Green Lantern is. Abin says that the ring will explain, and then he dies.
The ring flies onto Hal's finger, and instantly all the data from the opening is uploaded into his head. Footage from the camera on Abin's ship then plays. It shows Abin taking Atrocitus from Shard. His plan was to take him to Oa so that the Guardians could question him about something. However, his warp drive malfunctions and he ends up above Earth's atmosphere. While he tries to fix the systems, Atrocitus frees himself. He rips Abin in half, and throws his upper body out of the ship (presumably eating his lower body off-screen).
The video stops playing, and Hal calls Carol to tell her to pick up. Carol drives to get Hal, but seconds before she arrives, Hal's molecules rip apart, and he is transported to Oa, where he discovers that he has a green uniform on similar to Abin's. Meanwhile, Carol, who saw the teleportation beam, assumes Hal is dead.
Atrocitus fixes the warp drive and flies back to Shard, where he tells the four that they will other prisoners that together they will start a new Lantern Corps under his command. Qull questions Atrocitus about why he should be leader, and Atrocitus says that he killed the greatest Green Lantern of all. Qull argues that any of them could have done it. Atrocitus frees Qull, strangles him, walks off-screen and presumably eats Qull. We then see Atrocitus using some of Abin Sur and Qull's bone and blood, as well as some pieces of the ground on Shard and the nails crucifying him and his cohorts, and he casts them into a fire. He then forms Red Lantern rings from this. He gives rings to the others, and they set off to find other members for their group.
Meanwhile, on Oa, Hal meets Kilowog and Tomar-Re. Kilowog puts him through a vicious workout, until Sinestro comes up and tells Kilowog that the Guardians have made him Hal's new trainer. Kilowog angrily leaves, and Sinestro trains Hal until it is time for Abin's funeral. Hal notices that one of the people at the funeral isn't a Lantern. This is revealed to be Abin Sur's son, Amon. Amon is secretly furious that Hal became Abin's successor instead of him. After the funeral, Hal is thrust back to Earth where he sees Carol crying. She sees Hal, and tells him that she thought he was dead. The two both admit that they are in love with each other.
Amon is seen returning home in his ship, when his ship goes through warp drive unexpectedly and he ends up on Shard. He is offered a position with the Red Lanterns, and accepts. He is asked who replaced Abin, and says that he is an earthling, and then remembers that his name is Hal Jordan. Amon wants to kill Hal, but Atrocitus says they must wait until the right time. He sends Zox and Bleez to Earth to cause chaos and to test Hal's abilities.
That night, Hal is at Carl Ferris's (Carol's dad) birthday party. THere are over a hundred people at the party. Hal goes inside to use the restroom and when he returns, he sees Zox and Bleez attacking the party. Discreetly he suits up as GL and fights the bad guys. However, the two Reds start flipping cars off the road, causing explosions. Hal stops most of the cars, but one still crashes. Hal saves most of the people, but two or three still die.
Hal is discouraged because people died but Carol and Hal's friend, Tom, remind him that he still saved most. Hal still is unsure of his capability.
Amon goes to Earth where he sees Hal with Carol, and so he breaks through the window and grabs Carol. When Hal wakes up, he discovers that Carol is gone. Hal tries to suit up, and discovers that his ring is out of power. He doesn't remember how to recharge it, but then he remembers the lantern Abin had with him.
He gets the lantern, and sets out to find Amon. He sees news footage of Amon dangling Carol from Coast Central Tower, the tallest building in the city, and Amon says that the woman will be spared if Hal surrenders. He goes, and finds Amon. He uses a baseball bat and knocks Amon off the building. This causes Carol to fall, but he creates a plane to catch her. He fights Amon throughout the city until Sinestro shows up. Sinestro helps Hal fight Amon. Eventually, Sinestro just stabs Amon and kills him.
The two lanterns are pulled back to Oa. Sinestro is exiled from the Corps for his actions, despite claiming that if the Reds are going to kill, so should they. Just after he leaves, the entire Red Lantern Corps, numbering in the thousands now, attacks Oa. Zox attacks Hal and after a long battle, Hal thrusts him straight into Bleez, knocking the two Reds off a cliff. Hal creates a jail cell to hold them. Hal then sees Atrocitus attacking the Guardians, and Hal creates a rocket around him, and blasts him away from the Guardians. Hal flies after Atrocitus, and the two battle across Oa. Finally, Kilowog comes and uses the same routine on Atrocitus that he used on Hal. Atrocitus, exhausted and distracted, is then taken by Hal, Kilowog, Tomar, Jack T. Chance, and Boodika to Guardian HQ, where the Guardians attempt to transport him back to Shard, but Atrocitus attempts to escape, causing the machine to malfunction, and trapping him in the core of Pluto. The Lanterns reward Hal and give him a chapter in the Book of Oa for his efforts.
In a post-credit scene, Sinestro is shown. He says "The Guardians just think the can exile me! Well, I'll be back, and when I am, I'll make sure they FEAR the name Sinestro." His eyes then glow yellow.