- Iron Man (Tony Stark) (Main story and flashback)
- Stark Industries
- Iron Legion (First appearance)
- Iron Patriot (Col. James "Rhodey" Rhodes) (First appearance as Iron Patriot)
- Harley Keener (First appearance)
- A.I.M. (First appearance) (Main story and flashback)
- Dr. Maya Hansen (Only appearance; dies) (Main story and flashback)
- Aldrich Killian (Only appearance; dies) (Main story and flashback)
- Extremis Soldiers (First appearance)
- Mandarin (Trevor Slattery) (First appearance)
- Vice President Rodriguez (First appearance)
- Dr. Ho Yinsen (First appearance chronologically)
- Doctor Wu (First appearance)
- Bambi Arbogast (Behind the scenes)
- President Ellis (First appearance)
- Joan Rivers (On-screen)
- Bill Maher (On-screen)
- Chitauri (Mentioned)
- S.H.I.E.L.D. (Mentioned)
- The Avengers (Mentioned)
- Roxxon Oil Corporation
- Thomas Richards (Only appearance; apparently dies)
- Mrs. Davis (First appearance)
- Homeland Security (Mentioned)
- Stan Lee
- Gary (First appearance)
- Thor (Mentioned)
- Dr. Bruce Banner (Cameo)
Races and Species:
- United States of America
- Colorado (Mentioned)
- Sandy Creek (Mentioned)
- Washington, D.C.
- Switzerland (Only in flashback)
- Bern (Only in flashback)
- Afghanistan (Mentioned)
- Kuwait (Mentioned)
- Ali Al Salem Air Base (Mentioned)
- United States of America
- Iron Man Armor
- MK I (Destruction)
- MK II (Destruction)
- MK III (Destruction)
- MK IV (Destruction)
- MK V (Destruction)
- MK VI (Destruction)
- MK VII (Main story and flashback) (Destruction)
- Mark VIII (First appearance) (Destruction)
- Mark IX (First appearance) (Destruction)
- Mark X (First appearance) (Destruction)
- Mark XI (First appearance) (Destruction)
- Mark XII (First appearance) (Destruction)
- Mark XIII (First appearance) (Destruction)
- Mark XIV (First appearance) (Destruction)
- Mark XV (First appearance) (Destruction)
- Mark XVI (First appearance) (Destruction)
- Mark XVII (First appearance) (Destruction)
- Mark XVIII (First appearance) (Destruction)
- Mark XIX (First appearance) (Destruction)
- Mark XX (First appearance) (Destruction)
- Mark XXI (First appearance) (Destruction)
- Mark XXII (First appearance) (Destruction)
- Mark XXIII (First appearance) (Destruction)
- Mark XXIV (First appearance) (Destruction)
- Mark XXV (First appearance) (Destruction)
- Mark XXVI (First appearance) (Destruction)
- Mark XXVII (First appearance) (Destruction)
- Mark XXVIII (First appearance) (Destruction)
- Mark XXIX (First appearance) (Destruction)
- Mark XXX (First appearance) (Destruction)
- Mark XXXI (First appearance) (Destruction)
- Mark XXXII (First appearance) (Destruction)
- Mark XXXIII (First appearance) (Destruction)
- Mark XXXIV (First appearance) (Destruction)
- Mark XXXV (First appearance) (Destruction)
- Mark XXXVI (First appearance) (Destruction)
- Mark XXXVII (First appearance) (Destruction)
- Mark XXXVIII (First appearance) (Destruction)
- Mark XXXIX (First appearance) (Destruction)
- Mark XL (First appearance) (Destruction)
- Mark XLI (First appearance) (Destruction)
- Mark XLII (First appearance) (Destruction)
- Iron Patriot Armor (First appearance as Iron Patriot Armor)
- Extremis virus (First appearance)
- Arc Reactor (Disposed of)
- Tony Stark's New Element
- Mjolnir (Mentioned)
Tony Stark recalls a New Years Eve party in 1999 with scientist Maya Hansen, inventor of Extremis- an experimental regenerative treatment intended to allow recovery from crippling injuries. Disabled scientist Aldrich Killian offers them a place in his company, Advanced Idea Mechanics, but is turned down. Years later, Stark's experiences during the Chitauri invasion on New York are giving him panic attacks. Restless, he has built several Iron Man suits, creating friction with his girlfriend, Pepper Potts. A string of bombings by terrorist "the Mandarin" has left intelligence agencies bewildered by a lack of forensic evidence.
When Stark Industries security chief Happy Hogan is badly injured in one such attack, Stark overcomes his stupor and issues a televised threat to the Mandarin, who responds by destroying Stark's home with helicopter gunships. Potts and Hansen, who had come to warn them, survive the attack. Stark then finds himself in rural Tennessee after his artificial intelligence J.A.R.V.I.S. followed a flight plan from Stark's investigation into the Mandarin. Stark's experimental armor lacks sufficient power to return to California, and the world believes him dead.
Teaming with Harley, a precocious ten-year-old boy, Stark investigates the remains of a local explosion bearing the hallmarks of a Mandarin attack. He discovers the "bombings" were triggered by soldiers subjected to Extremis, which at this stage of development can cause certain subjects to explosively reject it. After veterans started exploding, their deaths were used to cover up Extremis' flaws by manufacturing a terrorist plot. Stark witnesses Extremis firsthand when Mandarin agents Ellen Brandt and Eric Savin attack him. With Harley's help, Stark traces the Mandarin to Miami and infiltrates his headquarters using improvised weapons. Inside he discovers the Mandarin is actually a British actor, Trevor Slattery, who says that he is oblivious to the actions carried out in his name.
The Mandarin is a creation of Killian, who appropriated Hansen's Extremis research as a cure for his own disability and expanded the program to include injured war veterans. After capturing Stark, Killian reveals he is the true Mandarin; he has kidnapped Potts and subjected her to Extremis, intending to infuse her with superhuman abilities and turn her against Stark as leverage to gain Stark's aid in fixing Extremis' flaws. Killian kills Maya when she has a change of heart about the plan.
Killian has also manipulated American intelligence agencies regarding the Mandarin's location, luring James Rhodes—the former War Machine, now re-branded as the Iron Patriot—into a trap to steal the armor. Stark escapes and reunites with Rhodes, discovering that Killian intends to attack President Ellis aboard Air Force One. Remotely controlling his Iron Man armor, Stark saves some surviving passengers and crew but cannot stop Killian from abducting Ellis. They trace Killian to an impounded oil drilling platform where Killian intends to kill Ellis on live television. The vice president will become a puppet leader, following Killian's orders in exchange for Extremis to cure his daughter's disability.
On the platform, Stark goes to save Potts, and Rhodes saves the president. Stark summons each of his Iron Man suits, controlled remotely by J.A.R.V.I.S., to provide air support. Rhodes secures the president and leads him to safety, while Stark discovers Potts has survived the Extremis procedure. However, before he can save her, a rig collapses around them and she falls to her apparent death. Stark confronts Killian and traps him in an Iron Man suit that self-destructs, but fails to kill him. Potts, whose Extremis powers allowed her to survive her fall, intervenes and kills Killian.
After the battle, Stark orders J.A.R.V.I.S. to destroy each Iron Man suit under Operation Clean Slate protocol as a sign of his intention to devote more time to Potts. The vice president and Slattery are arrested for their crimes. With Stark's help, Potts' Extremis effects are stabilized, and Stark undergoes surgery to remove the shrapnel embedded near his heart. He pitches his obsolete chest arc reactor into the sea, musing he will always be Iron Man.
In the present, Stark wakes up Dr. Bruce Banner, who fell asleep listening at the beginning of Stark's story.
A final title card reads Tony Stark will return.
- Robert Downey Jr. as Iron Man / Tony Stark
- Gwyneth Paltrow as Pepper Potts
- Don Cheadle as Iron Patriot / Colonel James Rhodes
- Guy Pearce as Aldrich Killian
- Rebecca Hall as Dr. Maya Hansen
- Stephanie Szostak as Ellen Brandt
- James Badge Dale as Eric Savin
- William Sadler as President Ellis
- Miguel Ferrer as Vice President Rodriguez
- Jon Favreau as Happy Hogan
- Ben Kingsley as The Mandarin / Trevor Slattery
- Dale Dickey as Mrs. Davis
- Ty Simpkins as Harley Keener
Paul Bettany and Shaun Toub reprise their roles as J.A.R.V.I.S. and Ho Yinsen. Wang Xueqi and Fan Bingbing portray Doctor Wu and his assistant in scenes shot specifically for the Chinese version of the film. Wang makes two brief appearances as Dr. Wu at the beginning and end of the film. Ashley Hamilton portrays Taggart. Spencer Garrett appears as a Rose Hill sheriff. Tom Virtue portrays Thomas Richards. Stan Lee and Adam Pally make cameos as a beauty pageant judge and as Gary. Rebecca Mader appears as a Ten Rings agent. Mark Ruffalo makes an uncredited cameo in the post-credits scene as Bruce Banner.
- Although Jon Favreau did not return to direct Iron Man 3, he still appears as Happy Hogan and retains his role as executive producer.
- Wang Xueqi was initially reported to be playing a character named Chen Lu, better known in the comics as the supervillain Radioactive Man.
- The film was under the working title, Caged Heat. This name has also been used as a distribution alias for the Iron Man 3 digital content packages. The working title of Iron Man 3 was later referenced in the Marvel One-Shot: All Hail the King, when it was used as the name given to a TV series in which Trevor Slattery played the main role of its rejected pilot.
- This film became the 17th film to pass $1 billion at the worldwide box office. With a worldwide total box office gross of about $1.2 billion, this film became the second-highest-grossing film of 2013, and at its peak the 6th-highest-grossing film of all time.
- Director Shane Black previously directed Robert Downey Jr. for the 2005 noir comedy Kiss Kiss Bang Bang.
- Early into the development, Nikolaj Coster-Waldau was considered for the role of Aldich Killian.
- Emilia Clarke of Game of Thrones fame was originally cast in the movie. Her role was dropped seemingly due to script changes.
- According to himself, Stan Lee was originally going to have a more prominent appearance. In a deleted scene from the Marvel Cinematic Universe: Phase Two Collection, it can be seen that Stan Lee's cameo would've had him holding a sign rating a beauty pageant contestant before he even had to, with one of the fellow juries telling him to put it down. Lee would also have been one of the victims of the tear gas Tony Stark would've used to clear the place to use the communications satellite.
- In early drafts of the movie, the main antagonist was going to be female. According to Shane Black, he was told by corporates to change the gender of the villain. A female villain pulling the strings behind a male villain was inspired by the TV series Remington Steele.
- A Hulkbuster Armor was originally going to appear as part of the Iron Legion, but it was eliminated to save the suit for a more featured role.
- Pearce and Black originally wanted to have Happy Hogan watching UFC in the hospital as a nod to the Jon Favreau's role in the sitcom Friends. The idea of using Downton Abbey came from Favreau himself. According to him, the scene of the series shown at Happy Hogan's hospital room was carefully chosen. Said scene features characters Tom Barrow and Sybil Crawley, a chauffeur and the woman of high society he longs for, which could symbolize that Happy secretly harbors feelings for Pepper. In the comics, Happy and Pepper had a romance and were even married.