A strange lightning storm appears in space, prompting the Federation starship Kelvin to investigate. In short order, a Romulan vessel – the Narada – emerges from the black hole at the heart of the storm and cripples the Kelvin. The Romulans “invite” their captain – Richard Robau – aboard to negotiate a truce. Once there, he is taken to their commander, Nero, who questions Robau about the whereabouts of Ambassador Spock, who he has never heard of. Nero then asks for the current stardate. Upon realizing that they’ve arrived a century and a half in the past (and several years too early), Nero kills Robau and resumes the attack on the Kelvin. First officer George Kirk gives the order to evacuate the ship, says goodbye to his wife (who is busy giving birth to their son – James Tiberius Kirk), and sets the Kelvin on a collision course with the Narada, given the survivors time to escape.
As Kirk grows into a rebellious youth on Earth, a young Spock is tormented by his peers on Vulcan, a result of his half-human heritage. Years later, Spock declines an offer of admission to the Vulcan Science Academy, instead entering Starfleet Academy. On Earth, later still, Kirk drunkenly flirts with a Starfleet cadet named Uhura at an Iowa bar before getting into a fight with another group of cadets. The fight is broken up by Captain Pike, who is aware of Kirk’s family history. Pike talks with Kirk and encourages him to join Starfleet. Though he is initially dismissive, he ultimately does just that.
On the shuttle to the Academy, he meets Leonard McCoy, a disgruntled doctor who decided to join Starfleet in the wake of a nasty divorce. Three years later, the Narada waits as a small starship emerges from a lightning storm anomaly. Nero recognizes it as belonging to Ambassador Spock and orders its capture. Back on Earth, Kirk is determined to pass the Kobayashi Maru test, though the whole point of the test is that there’s no way to win. The day of the test, Kirk conducts himself in a theatrically cavalier manner, but he does pass, to the surprise and confusion of the observers – among them, Spock.
A formal inquiry follows, and Kirk is accused by Spock of cheating. As he tries to defend himself, the hearing is interrupted by news of a distress call from Vulcan that followed the appearance of a lightning storm. With the primary fleet occupied, Starfleet begins commissioning cadets to crew every ship available.
Cadets are assigned based on aptitude, with the best and brightest being posted the newly constructed USS Enterprise under the command of Captain Pike. Kirk is grounded due to the disciplinary proceedings but, recognizing the lightning storm as similar to the one that occurred when he was born, is determined to accompany the fleet. McCoy fakes a medical emergency in order to bring Kirk aboard the Enterprise with him. Once her crew arrives, the Enterprise gets underway, with orders to investigate seismic disturbances on Vulcan and assist in the evacuation of the planet if necessary. The more he learns, the more convinced Kirk is that they are walking into a trap and rushes to the bridge to warn Pike.
They arrive at Vulcan to find the fleet destroyed and the Narada drilling into the planet. The Romulans attack, but Nero orders a ceasefire when he realizes which ship he’s attacking. He hails the damaged Enterprise, greets a confused Spock, and – much as he did with the Kelvin’s captain – orders Pike to take a shuttle and come aboard the Narada. Pike agrees leaving Spock in command and assigning Kirk as first officer. While he heads for the Narada, Kirk, Sulu, and Chief Engineer Olson will skydive to the drilling platform (which in addition to threatening Vulcan is interfering with the Enterprise’s transporters and preventing them from contacting Starfleet) and disable it. And despite Olson’s death, they succeed at stopping the drill. But it turns out they weren’t quick enough, as the Romulans are still able to inject a red matter payload into the core of the planet. As they do so, Chekov realizes that the Romulans are using the red matter to create an artificial black hole in Vulcan’s core. Realizing the planet is doomed, Spock signals an evacuation and beams down to rescue the Vulcan Council, which includes his parents. He is only partially successful, retrieving most of the Council but failing to save his mother.
The Enterprise retreats to a safe distance and the crew watch in horror as Vulcan implodes. On the Narada, Nero tortures Pike in an effort to gain the security codes to Earth’s defense systems. As he does so, he explains that in his time, the Narada was originally a mining ship, that he is driven by the loss of his wife and unborn child who were killed in the destruction of Romulus, which he blames on the Federation’s inaction and an unspecified betrayal by Spock. He now intends to destroy the Federation world by world so that others will know his pain.
On the Enterprise, Spock reasons that Nero is from the future and determines that the best course of action is to regroup with the fleet. Kirk disagrees, saying that the best way to stop Nero is to simply go after him. They argue, Spock orders Kirk removed from the bridge, and when Kirk resists, Spock incapacitates him with a nerve pinch and orders him jettisoned in an escape pod. Kirk awakens in the pod, having already landed on the snow-covered planet Delta Vega. Kirk grabs his gear and heads for the nearest Starfleet outpost. On the way, the local wildlife chases him into a cave where he is rescued by… Spock. That is, the Spock from Nero’s time, a hundred and twenty-nine years in the future.
Spock mind melds with Kirk to give him the backstory: In the late twenty-fourth century, a supernova threatened the homeworlds of the Romulan Empire. Spock devised a plan to use red matter to create an artificial singularity and essentially counteract the nova. However, he arrived too late and the star exploded, destroying Romulus. He launched the red matter hoping to mitigate the damage and was immediately confronted by Nero. The black hole created by the red matter created a disturbance in space-time and pulled both of their ships in, depositing them in the past. Nero’s attack on the Kelvin created an alternate timeline. When Spock arrived, he was captured by Nero and marooned on Delta Vega to give him a front row seat to Vulcan’s destruction.
Spock then leads Kirk to the Starfleet base where they meet Keenser and this timeline’s version of Scotty, who says he was “exiled” here after a failed experiment in transwarp beaming. Spock advises Kirk to relieve his younger self of command by provoking him, thus demonstrating how emotionally compromised he is. With Spock’s help, Scotty is able to beam himself and Kirk to the Enterprise, where Kirk picks a fight with Spock, who beats him like the red-headed stepchild of a rented mule before coming to his senses and relinquishing command. Kirk takes over and sets about chasing Nero to Earth.
While en route, Chekov devises a plan to conceal their approach from Nero. Spock, having cooled down, returns to the bridge and volunteers to beam aboard the Narada to retrieve the black hole device. Kirk agrees and says he’ll be going along as well to rescue Pike. The Enterprise arrives just as the Narada begins drilling into San Fransisco Bay. Kirk and Spock beam over and, after a firefight, track the black hole device to the elder Spock’s ship, the Jellyfish, which recognizes the younger Spock as its captain. Spock commandeers the Jellyfish and uses it to destroy the drill while Kirk confronts Nero. Nero has the upper hand but storms off upon receiving word of the drill’s destruction, leaving Kirk to his second in command, who doesn’t fare so well.
Spock baits Nero into pursuing the Jellyfish into deep space. Realizing that Spock intends to ram the Narada and ignite the red matter to create a black hole, Nero panics, bombarding the smaller ship with weapons fire. Spock is saved by the timely arrival of the Enterprise and is beamed aboard – along with Kirk and an injured Pike – before the collision.
The black hole destroys the Narada – with a little help from the Enterprise’s photon torpedoes. The Enterprise is caught in the black hole’s gravity, Scotty is able to blow them clear by ejecting and detonating the warp core. Back on Earth, the two Spock’s meet and the ambassador gives his younger self some advice before leaving to help rebuild Vulcan civilization. Kirk is promoted to captain and given command of the Enterprise while a recovering Pike is himself promoted to the Admiralty. The crew assembles, and the Enterprise embarks on its mission of exploration.