In Malibu California, Tony Stark has insomnia and over 72 hours he develops the new prototype MK42 of the Iron Man armature. He also recalls events in 1999, in Bern, Switzerland, when he had one night stand with the genetic scientist Maya Hansen that was researching a regenerative process and made fun of his fan Aldrich Killian on the New Year eve. There are explosions in Los Angeles and the terrorist Mandarin assumes the attempts broadcasting through television. When Tony's bodyguard and friend Happy Hogan is seriously wounded in an explosion, Tony Stark challenges Mandarin and gives his address to him. However, three helicopters attack his mansion and he loses everything but his prototype, and he awakes in the Tennessee. Tony tries to make work the defective prototype and soon he discovers that the event from 1999 is connected to the present terrorist attacks.
- Robert Downey, Jr. as Tony
Stark / Iron Man:
A self-described billionaire, genius, playboy and philanthropist, who is one of the founding member of The Avengers, and is famously known as the super-hero Iron Man through high-tech suits of armor of his own invention.
- Gwyneth Paltrow as Pepper Potts:
Stark's girlfriend, long time associate and personal assistant. Potts is a victim to the Extremis experiment and gains superpowers until she gets surgery to remove Extremis from her body.
- Don
Cheadle as USAF Lt. Col. James "Rhodey" Rhodes / Iron
Patriot: Stark's best friend, the liaison between Stark
Industries and the U.S. Air Force in the department of acquisitions and
the operator of the War Machine armor.
- Guy
Pearce as Aldrich Killian /Firebrand: The
main antagonist of the film. He is the creator of The Extremis
Virus. Only in this film, he will become just like Mallen and fight Iron
Man at the docks.
- Rebecca
Hall as Maya Hansen: A botanist,
Stark's former girlfried, and the creator of the Extremis Virus. Hansen
worked for A.I.M. alongside Killian.
- James Badge Dale as Eric
Savin: Aldrich Killian's henchman, who was injected by
Extremis.
- Stephanie Szostak as Ellen
Brandt: One of Killian's best henchwoman . A war
veteran, injected by Extremis and is now a deadly assassin.
- Jon
Favreau as Happy Hogan: Tony's good
friend and his former personal bodyguard. He reprised his role in Iron Man
3.
- Ben
Kingsley as The Mandarin / Trevor Slattery: A supporting
antagonist of the film. Though traditionally the Mandarin is portrayed as
Iron Man's arch-nemesis in the comics, he will be portrayed as the leader
of the Ten Rings to cover up Killian's "experimental"
explosions.
- Ty
Simpkins as Harley Keener: A precocious 10-year
old boy who helps Tony in his mission to find and stop the Mandarin.