- "According to Stane, Stark pulled the old files on an alloy his father worked on during World War II... for an OSS op called Project: Rebirth."
"I can guess what happened next. Stark found an...example...of the alloy in his father's archives and used it to strengthen his suit."
- ―Phil Coulson and Nick Fury
The Mark III Armor was Tony Stark's third Iron Man suit and an upgrade from the Mark II, improving on its previous flaws. It was the first suit to integrate an advanced on-board weapons system and was the first to adopt the standard red and gold color scheme.
After nearly perfecting his Mark II armor, Tony Stark discovered a nearly fatal icing problem in the suit during a high altitude test flight after which he decided to move on to develop the Mark III suit. Stark later solved the suit's icing problem by using a gold-titanium alloy from an earlier satellite design that wasn't prone to freezing. He also opted to integrate a new, miniaturized weapons system that was concealed by the suit's exterior plating. Once the armor was ready for assembly J.A.R.V.I.S showed Stark a preview of the finalized design. Stark disliked the armor's new coloring due to the new materials used so he personalized it with a red paint job.
After learning that his supposedly discontinued weapons, including a set of his Jericho missiles, were being used by the Ten Rings to terrorize Gulmira, the home village of Ho Yinsen, Tony watch a news report about it enraged as he worked on the Mark III's repulsors. While doing so he accidentally discovered the palm repulsors can be used as offensive weapons. Stark doned the armor and went off to fight the terrorists.
Stark arrived at Gulmira and swiftly defeated the Ten Rings that held him hostage before and destroyed all of their weapons. Doing so however called the military's attention so they sent two F-22 fighter jets to investigate. Stark tried to evade and lose the jets but accidentally downed one of the after crashing into its wing, prompting the military to step up its assault. However, Stark was able to prove he isn't a threat after revealing his identity to his friend Lt. Colonel James Rhodes and saving the pilot of the downed F-22, whose parachute didn't deploy upon ejecting. The whole incident was later written off to the public as "an unfortunate training accident". Raza noticed the armor and quickly figured it was Tony with an improved version of the armor he used to escape.
Some time later, Tony Stark was confronted by Obadiah Stane, who paralyzed him with a sonic device and took the advanced arc reactor from his chest in order to power his own reversed engineered Iron Monger Armor. After struggling to retrieve his older arc reactor to save his life, Stark suited up in the Mark III and flew to the Stark Industries building to confront Stane and save Pepper Potts. Despite having to use the older, weaker arc reactor, Tony Stark was able to hold his own against Stane's heavier, weapons-laden suit as their battle spread to the nearby streets. In an attempt to trick Stane, Stark flew up into the upper atmosphere with Iron Monger following behind him. However, Stane's suit began to freeze over, having failed to account for the icing problem Stark faced with the Mark II suit, and promptly shuts down and falls back to earth. Stark landed on the roof of the Stark Industries building, running dangerously low on power, but Stane reappeared to confront him. While sabotaging Obadiah's suit Tony instructs Pepper to overload the giant arc reactor that powers the Stark Industries building. After luring Stane over the arc reactor, Pepper detonated it releasing a massive amount of energy into the atmosphere, subsequently killing Stane, leaving Tony Stark nearly dead, and the Mark III in shambles.
After the fight with Iron Monger, the Mark III was labeled battle damaged and, believed to be beyond repair, was subsequently replaced by the Mark IV suit. It was however displayed, still semi-damaged, in Stark's Hall of Armor with his other suits. 
The Mark III was destroyed when Tony Stark's Mansion came under attack by Mandarin's forces. Damage to the mansion's systems cause the suit to unintentionally detonate (possibly an overload of the miniature arc reactor).
The Mark III made a number of advancements from the previous Mark II, mainly solving the design flaws the prototype armor showed during it's test run, and creating a new standard from which his later suits were created. Tony Stark was able to solve the icing problem, which was the biggest design flaw of the Mark II, by substituting the same metal that was used in Stark tactical satellites, which was far less prone to freezing, into the suit's new design. The suit now allowed Tony to speak on the phone using his own cellular's phone number, however if used when flying the loud noise of the wind made it difficult for Tony to hear the other speaker.
Like the previous suits, the Mark III enhanced the user's physical capabilities, granting them near superhuman level strength (which the Mark III proved is enough to lift a car), near bullet-proof durability, and enhanced movement speed and reflexes.
In addition to the other advancements, Stark also decided to integrate his own advanced, miniaturized weapons system concealed beneath the suit's exterior plating. This included a set of mini-guns concealed in the shoulders of the suit that could fire a total of twelve shots at a time, six from each shoulder, and used a computer guiding system to fire at multiple individual enemies, in different positions, at the same time. The suit contained a small set of miniaturized, high explosive missiles, concealed in each forearm, each capable of taking out a full size tank.
The Mark III also contained a set of non-weaponized flares contained in two circular launchers located at the suit's hips. Stark has used these in at least two occasions: to distract the two F-22s that were pursuing him in the skies over Gulmira, and to temporarily blind the Iron Monger in their fight.
In addition to the other weapons, Stark upgraded the energy output of his repulsors to weapons grade levels after which they have become the standard weapons of every Iron Man armor since. Stark also modified the suit to fire unibeams or beams of concentrated energy, siphoned straight from the arc reactor, and shot through the aperture on the suit's chest. 
| Mark I • Mark II • Mark III • Mark IV • Mark V • Mark VI • Mark VII|
Mark VIII • Mark IX • Mark X • Mark XI • Mark XII • Mark XIII • Mark XIV • Mark XV • Mark XVI • Mark XVII •
Mark XVIII • Mark XIX • Mark XX • Mark XXI • Mark XXII • Mark XXIII • Mark XXIV • Mark XXV • Mark XXVI •
Mark XXVII • Mark XXVIII • Mark XXIX • Mark XXX • Mark XXXI • Mark XXXII • Mark XXXIII • Mark XXXIV •
Mark XXXV • Mark XXXVI • Mark XXXVII • Mark XXXVIII • Mark XXXIX • Mark XL • Mark XLI
Mark XLII • Mark XLIII • Mark XLIV/Veronica • Mark XLV • Mark XLVI
|Mark I • Mark II/Iron Patriot • Mark III|
|Mark I • Mark II|