The Arc Reactor was a device initially designed by Howard Stark, and later adapted by his son, Tony. A massive arc reactor provided power for the sprawling complex of Stark Industries until its destruction, and now the Stark Tower. This design was miniaturized by Tony to power a life-saving electromagnet in his chest, which had an energy output of 8 gigajoules per second.

Further upgrades to the design allowed Stark to employ successive generations of arc reactors, most notably in powering his crowning achievement, the Iron Man armor. Early generations of Iron Man armor were powered by much the same arc reactor technology as had powered Stark's electromagnet device, however poisoning from the palladium within the reactors were having an adverse effect on his health. This forced a radical redesign whereby Tony created a new element previously only theorized by his father years earlier. This new arc reactor had a massive power output advantage over previous arc reactors and was the first to power the formidable Iron Man MK VI armor.

Since their inception, mini-arc reactors have powered successive generations of the Iron Man armor as a force for good. They have also fallen into the hands of far less savory individuals and used to power further battle suits for criminal operations, and a fleet of robotic battle drones.

Stark had the arc reactor in his chest removed after receiving surgery to remove the shrapnel from his chest. He later removed the element and then threw the decommissioned unit into the ocean.

Stark soon returned to building arc reactor technology and used a number of them to power later generations of Iron Man.

Later generations of the Iron Man armor contained multiple arc reactors within one suit.