Seamus O'Rourke is the main antagonist in the 1998 film Ronin.
Seamus is an Irish terrorist and boss to an IRA (Provisional Irish Republican Army) operative named Deirdre. Seamus' goal is to acquire a large metallic case (the contents of which is unknown) that is being held by a heavily armed convoy and sell it, and he makes Deirdre hire a group of mercenaries to steal the case for him. As the mercenary group chase after the men holding the case and a fierce gunfight ensues, one of the group members, named Gregor, betrays the other men by leaving them with a fake case that is rigged to explode. One of the other mercenaries, named Sam, gives chase but Gregor escapes, only to be captured by Seamus. He, Gregor and Deirdre escape in a car and return to one of Seamus' safe houses, where he beats Gregor for information on where the real case is being contained.
Gregor leads Seamus and Deirdre to a post office where he finally obtains the case, but is then pursued by Sam and his associate Vincent. After a furious car chase, Deirdre crashes her car after Vincent shoots out her tires, though she and Seamus are rescued by a group of bystanders before the car explodes (while Gregor flees). Sam and Vincent track down Gregor once again, leading them to a large arena where Gregor is making a deal with a Russian mobster. Before Sam arrives, the mobster kills Gregor and takes the case from him. Outside the arena, Seamus appears and kills the mobster before stealing the case back from him. Vincent is wounded by Seamus as Sam chases after him, but Seamus gains the upper hand and holds Sam at gunpoint. Before he can fire, Vincent fatally shoots him, saving Sam's life.