In this "origins" look at the beginnings of the story of the Starship U.S.S. Enterprise and her crew, young James Tiberius Kirk is born just moments before his father, George Kirk (CHRIS HEMSWORTH), sacrifices himself to save everybody onboard the U.S.S. Kelvin that's just come under attack. The perpetrator is Romulan Captain Nero (ERIC BANA) who's out to avenge the death of his wife, child and others, for which he fully blames Ambassador Spock (LEONARD NIMOY).
Decades later, Kirk (CHRIS PINE) has grown up into a brash and impulsive young man in Iowa with a thing for bucking authority and hitting on pretty, young women such as Nyota Uhura (ZOE SALDANA), who wants nothing to do with him. The latter results in a bar fight between Kirk and some Starfleet Academy enrollees, only to be broken up by Captain Christopher Pike (BRUCE GREENWOOD). He sees untapped if unrefined potential in the young man, and eventually convinces him to attend the academy.
Yet, three years later, Kirk's impulsive behavior has kept him from being called to duty on any ship, particularly due to clashing with young academy instructor Spock (ZACHARY QUINTO). Having grown up bullied by his Vulcan brethren for having a Vulcan father and human mother, and trying to balance that internal combination of logic and emotion, Spock has little patience for Kirk and his ways of breaking the rules in order to win. But when a distress call comes from Vulcan and the yet-to-christened U.S.S. Enterprise is called into duty, Kirk ends up onboard, thanks to his medical officer friend, Leonard "Bones" McCoy (KARL URBAN), who induces a fake illness to pull that off.
Along with Pike and Spock, Kirk encounters the rest of the crew, including communications expert Uhura, helmsmen Hikaru Sulu (JOHN CHO), and navigator Pavel Chekov (ANTON YELCHIN). Upon arriving at Vulcan, Pike and his crew realize the planet as well as several Federation starships are under attack by Nero and his technologically advanced warship.
When things go badly there, Kirk ends up banished on an ice planet where he not only meets engineering expert Montgomery "Scotty" Scott (SIMON PEGG) but also a much older and wiser Spock, who gives him the lowdown on what's occurring. From that point on, Kirk does what he must to gain control of the Enterprise and prove his worth by defeating Nero and saving the day.