Spoiler Alert: In addition, also included is some extra info for some of the groups and characters; given the fact that this information gives away a large portion of the show, they have been rendered as blue text on a blue background. If you've already seen the entire show, or are itching to learn more, use your mouse pointer to highlight the text and make it visible.

The Bad Guys

The United Earth Alliance Sphere
After a series of international disputes, this international governing body is established to foster peace between warring nations on Earth. Though its original charter is to bring peace, the Alliance soon turns to oppression, enrolling nations against their will and crushing those who oppose the New World Order.
Around the time the Gundams attack as a part of Operation Meteor, General Noventa and other Alliance generals have grown weary of war and seek to make peace with the colonies, at which point the financial supporter of the Alliance decides to eliminate them and take over.

The Romefeller Foundation
On paper, this industry-military combine is the chief financial supporter of the Alliance, and their subsidiary OZ produces the humanoid machines for the Alliance's mobile suit corps, also known as the Specials.
In providing the Alliance with their main fighting vehicle, the Romefeller Foundation was also able to infiltrate the Alliance and take control; the Romefeller Foundation then uses its influence to steer the Alliance towards tyranny. Its chief executive is Duke Dermail, a money- and power-hungry individual who seeks world domination.

The Specials
The elite mobile suit corps within the Alliance Forces. Its ranks include their charismatic commander Treize Kushurinada, his sadistic aide Lady Une, and the masked ace Zechs Marquis, who has earned the nickname "Lightning Baron" for his excellent mobile suit piloting skills. In reality, this group serves as a secret presence of the Romefeller Foundation within the Alliance Forces; as their primary offensive division, the Specials also wield a large amount of influence in Alliance policy, and they use this influence to do the bidding of the Romefeller Foundation.

OZ
Originally the subsidiary of the Romefeller industry that produces mobile suits, in time it has become synonymous for Romefeller's secret society within the Alliance. When the Alliance attempts to steer from Romefeller's agenda and decides to negotiate peace with the colonies, OZ drops its "Specials" cover and takes over the Alliance in a coup d'etat.
Later, the Romefeller Foundation becomes dissatisfied with Treize's leadership and pressures him to resign, upon which OZ splits into Romefeller and Treize factions.

The World Nation
The Romefeller Foundation assumes control of Earth and declares itself The World Nation; to maintain a semblance of good will, Duke Dermail forces Relena to act as a figurehead and become Queen Relena of their World Nation.
In an unexpected move, Relena convinces the other Romefeller execs to strive for peace; now that they are in total control of the world, they can afford to be magnanimous. The executives are swayed by Relena's words, much to Duke Dermail's dismay. Later, when the evil Duke is killed, Treize steps in and convinces the Romefeller execs to put him in control of the World Nation, and takes over in a bloodless coup.

White Fang
As OZ makes a goodwill tour of the colonies, portraying themselves as the savior from the Alliance and routing the Alliance Forces from the colonies, a portion of OZ splits claiming to fight for the independence of the colonies in earnest. The group originally forms under Quinze, one of the principals behind Operation Meteor. When Milliardo leaves the OZ forces, Quinze recruits him to become the face and leader of White Fang. The gigantic space fortress Libra becomes their main base of operations.

The Barton Foundation
The entity that surfaces in the video series ENDLESS WALTZ. What is its connection to Gundam pilot, Trowa Barton?

Spoiler: The Barton Foundation is the organization responsible for planning Operation Meteor. Planned by Dekim Barton and coordinated by Quinze, the plan involves dropping a space colony on Earth to create a climatic catastrophe and global chaos. Then five super-advanced mobile suits, the Gundams, will be sent to Earth to seize control of the planet. The space colonists will thus become the rulers of the human race. However, Quinze was interested mainly in punishing Earth for Heero Yuy's death; the doctors shared his view but saw fit to alter the means. When Trowa Barton realizes this, he threatens to inform his father Dekim, and is shot and killed. A nameless mechanic working on the Heavy Arms volunteers to take his place, assuming the identity of Trowa Barton.

The Good Guys

Heero Yuy
When the colonies seek to peacefully oppose Alliance rule, they elect the charismatic Heero Yuy as their representative. His message of pacifism is well-received by many nations on Earth, and his leadership brings solidarity and unity to the colonies. Unfortunately, he is assassinated 10 years later, and the colonies plummet into chaos.
Twenty years later, the colonies send five Gundams down to Earth as a part of Operation Meteor. As a symbolic gesture, the pilot of the Wing Gundam is codenamed Heero Yuy, after the martyred space leader.

The Sanc Kingdom
This peaceful kingdom, an advocate of Heero Yuy's pacifism, is overrun by the Alliance during its years of oppression. During the attack, King Peacecraft is killed. His daughter Relena is rescued and adopted by his aide Darlian, but his son Milliardo disappears during the conflict.
Later, Relena attempts to resurrect the Sanc Kingdom and promote her views on pacifism and non-violence, and her school is attended by many students from around the world. One of them is Dorothy Catalonia, spying on Relena on behalf of her uncle and leader of the Romefeller Foundation, Duke Dermail.

The Doctors
These scientists by the code names of Doctor J, Professor G, Doktor S, Instructor H and Master 0. They are the chief developers of the prototype Leo; when Heero Yuy is assassinated, the five scientists quit the project and disappear. The prototype design is scaled down for mass production, while the original becomes the mobile suit known as the Tallgeese.
Later on, the five scientists develop the Wing Zero, but discard the design as too destructive and dangerous. Afterwards, they each design a Gundam for our heroes as a part of Operation Meteor.

The Gundam Pilots
These lethal and resourceful teens are trained professionals at piloting mobile suits, computer hacking, sabotage, and general mayhem. Most come from tragic backgrounds; Duo is an orphan whose friends either died from disease or were massacred in war, while Wu-Fei's wife Meirang died in battle while protecting their colony from an Alliance hit squad. Details on Heero and Trowa are sketchy at best, though the video release Endless Waltz provides a few glimpses into these brooding kids' past.
Of the party of five, Quatre comes across as the most even-mannered of the group; though he isn't as accomplished as a pilot, he is extremely wealthy and has plenty of family connections. In time, Quatre becomes the de-facto leader of the Gundam pilots as they prepare for their final battle against both the World Nation and White Fang...

The Sweeper Group
This salvage organization includes Howard and Professor G. Howard operates a salvage ship on Earth, and Duo is seen hanging around on Howard's ship on Earth between sorties. Howard and Professor G are also responsible for the construction of the huge spaceship Peacemillion.

The Maganac Corps
In AC 193, Quatre's shuttle is hijacked by a group of renegades, known as the Maganac corps, who seek to rescue abandoned workers on the resource satellite MO-III. Feeling drawn to the warm-hearted Maganac corps, Quatre aids them in their rescue mission, saving leader Rashid from a traitor and fending off Alliance Forces to guard their escape.
The eternally grateful Maganac corps have since sworn to protect and defend Quatre at all costs, even with their own lives. Their mobile suits are customized for each pilot, from oversized shoulder housings to giant crushing manipulators.

Preventer
This intelligence and operations agency is established after the end of the war between the World Nation and White Fang. Its mission is to investigate and prevent further conflicts from arising. They are first shown in ENDLESS WALTZ.

Spoiler: Preventer is led by Lady Une, who has discarded her sadistic persona and is now a sworn defender of peace. Working for her are former Alliance soldiers Sally Poe and Lucrecia Noin. When the Barton Foundation decides to give the original Operation Meteor a second try, Zechs Marquis reappears from the dead and joins the organization. Together, these former friends and enemies now fight for a just cause, and join the Gundam pilots in their struggle against the Barton Foundation.

Next: The Future of Gundam