The RX-78-2 Gundam is the titular mobile suit of Mobile Suit Gundam television series. Part of the RX-78 Gundam series, it was built in secret on Side 7. The Gundam would turn the tide of war in favor of the Earth Federation during the One Year War against the Principality of Zeon. It was primarily piloted by Amuro Ray.

The Gundam was incredibly advanced for its time. Built from lightweight Luna Titanium Alloy, its frame was both lighter than that of Zeon's mass-produced mobile suits and much sturdier, able to shrug off a MS-06 Zaku II's machine gun fire with little to no damage. Its offensive power was above and beyond that of the Zakus. The Gundam would engage in most battles with its beam rifle, making it the first mobile suit to have firepower equivalent to a battleship's beam cannons. In addition, it made use of two beam sabers, blades of extremely hot plasma which could cut through any metal with ease. Those beam sabers could be extended into a spear-like beam javelin, which could be used to stab into an enemy from a longer distance.

The Gundam also used more conventional weaponry; it could launch rockets with a "Hyper Bazooka", the Federation's answer to the bazookas used by Zeon's Zakus; in addition, its head was outfitted with a pair of small vulcan guns, as a way of attacking light-armored aircraft and vehicles without wasting ammo or energy from its more powerful armaments. It also made use of a very unconventional close-range weapon known as the "Gundam Hammer" - a large weapon similar to a flail which could be swung at enemies to deal crushing damage. The Gundam Hammer was eventually upgraded for use in space and outfitted with a number of verniers on the ball, and renamed to be the "Hyper Hammer". Lastly, it wielded a shield which would offer it a defense against enemy attacks that not even its Luna Titanium body could withstand without damage. Gundam pilot, Amuro Ray, would make use of the shield as a decoy in many battles, taking advantage of its size to fool the enemy into thinking he was charging at them, then attacking the enemy through the shield.

In terms of technology, the Gundam was equipped with a sophisticated Learning Computer which would collect pilot and enemy data during skirmishes and allow the Gundam to operate more effectively. The data from the computer was used by the Federation to improve the controls of the Gundam's mass-produced form, the RGM-79 GM. In addition, it was upgraded by Federation technician Mosque Han shortly before the Battle of A Baoa Qu to improve its reaction times, the joints of the Gundam were given a Magnet Coating, based on the experimental procedure performed on the RX-78-3 "G-3" Gundam and later used on Amuro's intended successor unit, the RX-78NT-1 Gundam "Alex".

The Gundam makes use of the Core Block System implemented in the other V Project units. The torso of the Gundam is mostly hollow so that a FF-X7 Core Fighter can dock with it. This allows the pilot to jettison the legs and torso of the Gundam should the machine be too heavily damaged and gives the pilot a chance to escape from battle. Later, during Operation Odessa, the Gundam is given a support unit known as the G-Fighter. The two G-Fighters were designed to take advantage of the Gundam's modular system and diversify the Gundam's role in active combat. These modes ranged from the assault bomber G-Armor to the close combat support tank G-Bull. Officially, it is called a prototype, but it is also said to be more of a custom-made machine that is finished with high quality materials and the best technology.