25 years earlier, Kazunori Yamauchi (Takehiro Hira) wanted to create a driving simulator to make racing accessible to the whole world. It would become known as Gran Turismo.
In Cardiff, Wales, Jann Mardenborough (Archie Madekewe) is a big fan of the Gran Turismo video games and has saved enough to buy himself a simulator. He lives with his parents, Steve (Djimon Hounsou) and Lesley (Geri Halliwell Horner), plus brother Coby (Daniel Puig), and works at a clothing store. Steve, a former footballer, does not support Jann’s endeavors to become a professional racer, seeing it as unrealistic and dangerous.
In Tokyo, Danny Moore (Orlando Bloom), a marketing executive for Nissan, arrives at a conference where he pitches to potential investors a contest for Gran Turismo players to have a chance to be real racers for Nissan, which would also possibly help boost car sales.
After the contest is signed off on, Danny seeks out professionals to teach the racers and is turned down by everyone until he reaches his last choice, former racer Jack Salter (David Harbour). Danny finds Jack working as a mechanic and pitches his idea to him, but Jack refuses, saying that putting gamers in real race cars could have potentially fatal consequences. Later, Jack is in a meeting with racer Nicky Capa (Josha Stradowski), an arrogant hothead up-and-comer. When Jack tries to give him a suggestion on keeping his emotions in check, Nicky calls him a has-been, so Jack calls Danny and decides to go ahead with the instructor position.
Jann later receives a message inviting him to compete in a simulated race after he played Gran Turismo at a gamer cafe, and his scored was logged in as being exceptional. A video from Danny states that the top racers will be invited to join the newly-established GT Academy for a chance to race for real.
Coby later tells Jann that he is going to an outdoor gathering with friends. Jann initially declines until Coby says that his crush Audrey (Maeve Courtier-Lilley) will be there. Jann goes and chats with Audrey, who wants to travel the world. The party is broken up by cops, forcing the teens to go home. While driving Steve’s car back, one of Jann and Coby’s friends gets a nearby car to pass them beer, only for the two cars to bump into each other, gaining the attention of police. After the other car gets pulled over, Jann hits the gas and drives away, leading to the police to pursue. After a brief chase, Jann is able to get the police off his tail, but he and Coby are dismayed to find Steve waiting for them at home, and Jann takes the blame for the damaged mirror.
Jann is brought to work with Steve at a railyard, mere moments before the simulated race is about to begin. Jann leaves and rides his bike to the cafe where he manages to make it on time to sign in. He begins to outrun the other players after utilizing the skills he has gained from playing at home, and he finishes in first place, qualifying him for the academy. Jann gets ready to leave, but is told by Steve once again that it is dangerous, but Jann reminds him that it was he who instilled a love of driving in him at a young age, and he is determined to prove everyone wrong.
Jann arrives at the GT Academy along with nine other potential racers, including the cocky Matty Davis (Darren Barnet). They are given a not-so-motivational speech by Jack, who still thinks this is a bad idea. The racers then begin to go through extensive driving exercises and physical training. Four of them get disqualified, and Jann is in danger of being next. During a driving round with Jack, he accidentally crashes, despite insisting he hit the brakes. Jack later learns that the brakes were indeed faulty, so he tells Jann that another racer has been eliminated so that he may enter the final race. Jann yells in excitement.
The racers get ready for the qualifying race. Jann places a sticker of his father’s football team on his helmet as a tribute to him. He begins the race in last place but quickly begins to make his way up to the front. As he gets closer to Matty, who is leading, Jann uses his tactics from playing the video game to ride alongside him, and it’s a close call to the finish line. Danny thinks Matty won, but Jack has them play the footage back to confirm that Jann won by a hair. Jann is moving on to bigger races, and his fellow racers, including Matty, congratulate him.
Jann travels with Jack and Danny to Austria to compete in races to qualify for an FIA license. He goes up against Nicky and other racers, starting off in dead last place. As Jann continues the races, he starts to move up, except for one where his car is knocked off-course by Nicky, so he doesn’t even finish. He has one more race in Dubai, where Jack tells him he needs to finish in at least fourth place to get his license. During the race, Jann manages to surpass Nicky, prompting the jerk driver to pick up too much speed and collide with another car. A tire from Nicky’s car flies toward Jann’s windshield but doesn’t damage it enough to prevent him from seeing, so he is able to finish fourth and gain his license.
Jann contacts Audrey and invites her to Tokyo to watch him officially get signed by Nissan. They spend the day together and end up at a dance club where they share their first kiss.
Jann then heads to the Nurburgring track in Germany for another race, which Steve and Lesley are watching at home. On the sixth lap, Jann manages to make it to second place, just before he drives too fast going up a hill, causing his car to flip over and go through a nasty crash. His parents become fearful after seeing it on TV, and Jann is taken to the hospital with Jack by his side.
After Jann wakes up, Danny and Jack inform him of what happened. A spectator was tragically killed in the crash, but they assure Jann that it wasn’t his fault. He begins to break down and says he wants to be left alone. He cannot even bring himself to speak to his parents, blaming himself for what happened.
Once Jann has fully recovered, Jack takes him for a drive to the spot where he crashed and he tells Jann what ended his racing career. He was driving at the Le Mans track and ended up in a wreck where another driver was killed. Jack quit racing after that and regretted it for not seeing how good he could have become, and he doesn’t want Jann to let the same thing happen to him. He lets Jann take the wheel so he can finish his lap.
Jann and Jack meet with Danny, who says that the other racing teams are trying to push for the end of having sim racers compete and are trying to build cases against them. They still plan to continue their competition at the 24 hour race in Le Mans with their own Nismo team, accompanied by Matty and fellow GT Academy driver Antonio Cruz (Pepe Barroso).
At Le Mans, Jann has his family, plus Audrey and other GT Academy drivers to come support him. Steve visits Jann as he is getting ready, and he apologizes for not showing him the support he needed earlier. The race commences, with Jann, Matty, and Antonio alternating driving hours. One rival driver ends up in a fiery crash, but he gets out of his car alive. When Jann goes up to drive, he starts to lose his focus after thinking about the crash. Jack helps by playing Kenny G and Enya to help Jann get his head back in the game.
On the final hour and lap of the race, Jann starts making his way to the front, having to outrace Nicky. He remembers driving the Le Mans track from the video games, and how he used his own method to surpass the other drivers. Using this same tactic, he is able to catch up to Nicky, where they are neck-and-neck racing toward the finish line until they make it there and JANN WINS! The whole team and his family head to the podium to celebrate while Nicky and his team accept their defeat.
The ending text states that Jann Mardenborough and Team Nissan’s victory at Le Mans changed motorsports forever. Jann has competed in over 200 races to date, and he even played his own stunt double in this film. Pictures of the real Jann and his family are shown alongside their film counterparts.