Plot

A year has passed since Eggsy Unwin (Taron Egerton) and the secret organization Kingsman saved the world from Richmond Valentine's neurological wave broadcast. He has since taken his late mentor Harry Hart's (Colin Firth) title of Galahad and lives with Crown Princess Tilde of Sweden (Hanna Alstrom). On his way home he is ambushed by Charlie Hesketh (Edward Holcroft), a formerly rejected Kingsman trainee who lost his arm and vocal cords during the Valentine incident. Eggsy manages to push Charlie into a Kingsman transport, disguised as a London cab.

Eggsy evades Charlie and his henchmen in a car chase across London, but Charlie's severed cybernetic arm hacks into the Kingsman servers through the car's computer system. Eggsy lures the pursuing cars into Hyde Park, which is a dark zone, and takes them out with missiles fired from the roof of the car.

Lancelot (Sophie Cookson) reveals that Charlie's associates during the chase (whom Eggsy killed), all had their teeth filed, fingerprints removed and had a golden circle tattooed on this chest. Her speculation is that they are dealing with a mafia organization.

Charlie passes the information to Poppy Adams - leader of the world's largest drug cartel, the Golden Circle - who launches a volley of missiles that destroy the Kingsman headquarters and wipe out all its agents in Britain, aside from Eggsy and Merlin, Kingsman's tech support. Eggsy was away in Sweden meeting Tilde's parents on the day of the attack. Tilde's father quizzes Eggsy on a wide range of topics from art, finance, politics, all of which Eggsy is able to answer with the help of Lancelot who was communicating with Eggsy through a minute device.

Poppy has the HQ in the middle of nowhere in Cambodia. Poppy's operatives have a circle tattooed on their chest, using a Golden ink. Poppy is a ruthless operator, who has 2 killer robot dogs at her command, and anyone who double crosses her is fed to the mince meat grinder.

Being the only surviving agents, Eggsy and Merlin (Mark Strong) follow the Doomsday protocol, which leads them to Statesman, a secret American organization posing as a Bourbon whiskey distillery in Kentucky as well as Kingsman's American counterpart. There, they discover that Harry survived Valentine's gunshot a year earlier using Statesman's Nanotechnology but is suffering from amnesia. Eggsy and Merlin are briefed by Statesman head Champagne (Jeff Bridges) about a secret terrorist organization called The Golden Circle.

They begin their mission by following Charlie's ex-girlfriend Clara Von Gluckfberg (Poppy Delevingne). When Statesman agent Tequila (Channing Tatum) develops blue rashes, he is replaced by agent Whiskey (Pedro Pascal) as Eggsy's partner. Meanwhile, Merlin and Statesman tech support specialist Ginger Ale helps cure Harry's amnesia.

At the Glastonbury Festival, Eggsy manages to plant a tracking device inside Clara, but his revelation of the mission to Princess Tilde strains their relationship. After several failed attempts to cure Harry's amnesia, Eggsy triggers Harry's memories by threatening to shoot a Cairn Terrier that resembles Harry's late dog.

Poppy Adams (Julianne Moore), head of world's largest drug cartel (& head of the Golden Circle), broadcasts a message telling the world about a toxin she laced within every recreational drug available, which causes users to develop blue rashes before progressing through mania, paralysis, and ultimately, death. She also demonstrates the antidote on a captive Elton John and offers it to the world if the President of the United States (Bruce Greenwood) ends his country's War on Drugs and offers her organization immunity.

The President believes that this is a brilliant plan to get rid of the planet of all criminal elements & decides to pretend to cooperate with Poppy, but in reality, decides to have every affected user quarantined so that they die in custody, including his Chief of Staff, Fox (Emily Watson). Eggsy, Harry, and Whiskey head to the antidote factory in Italy after intercepting a phone call to Charlie by Clara. Eggsy manages to steal an antidote sample, but it is broken by Whiskey during an ambush by The Golden Circle's henchmen. During the gunfight, Harry shoots Whiskey in the head, as he suspects that Whiskey is playing both sides, but Eggsy saves him with the same alpha-gel that Statesman had used to save Harry.

Simultaneously, Charlie destroys the antidote factory, killing Clara for unwittingly betraying the Golden Circle. Princess Tilde calls Eggsy in a state of mania, revealing that she has been affected by the blue rash. Eggsy, Harry, and Merlin discover the location of Poppy's hideout, "Poppy Land", in Cambodia and fly there to steal the remote control which deploys the antidote drones.

Upon their arrival at Poppy Land, Eggsy steps on a land mine, but is saved by Merlin, who sacrifices himself while taking the lair's guards with him. Eggsy and Harry storm through the lair and Eggsy kills Charlie while Harry destroys Poppy's robotic attack dogs with the help of Elton John who had been kidnapped by Poppy.

They secure the briefcase with the access code to the drones and inject Poppy with a more potent dose of her toxin. She gives them the password before succumbing to an overdose. Before they can activate the drones, they are stopped by Whiskey, who, having previously lost his wife to crossfire from two methamphetamine users, is revealed to be working alone to ensure that all drug users are eliminated. Furthermore, the elimination of all drugs will cause the stock price of Statesmen Whiskey to skyrocket since people will depend much more on alcohol, making Whiskey and his Statesmen members rich. Eggsy and Harry fight and kill Whiskey by pushing him into an industrial meat grinder, then deploy the drones to release the antidote, saving the millions of affected victims throughout the world.

In the aftermath, Chief of Staff Fox has the President impeached for conspiring to commit genocide on the drug victims. Champ announces that Statesman has acquired a distillery in Scotland to help rebuild Kingsman. To avoid the confusion of two Kingsman agents using the code-name "Galahad", Champagne offers either Eggsy or Harry the agent title of Whiskey, but they decline and Statesman tech support Ginger Ale (Halle Berry) steps in to take the role. Eggsy marries Princess Tilde, and Tequila moves to London to work for Kingsman, which acquires a new tailor shop in London.