Katharon (カタロン) is a prominent anti-Earth Sphere Federation military resistance organization formed in the wake of the advent of the A-Laws in Mobile Suit Gundam 00. Its member consist primarily of people from non-Earth Sphere Federation affiliated nations as well as those from the three major powers (the Union, Human Reform League, and AEU) that are dissatisfied with the Earth Sphere Federation's policies.
Due to the lack of GN Drive-equipped mobile suits available outside Federation control, Katharon is forced to make due with the almost horrendously outdated conventional mobile suits in comparison to the mobile weapons in the A-Laws' arsenal. It is believed that Katharon has secretly gained support from people outside the organization.
Each Katharon base is led by a division head or a council of people. Generally, Klaus Grad is the de facto leader, having lead Katharon's forces against the A-Laws in space.
- Klaus Grad - is the commander and the de facto leader of Katharon, which opposes the Earth Sphere Federation and its elite squad A-Laws.
- Shirin Bakhtiar - is the political adviser and coordinator to Princess Marina Ismail of Azadistan. After the formation of the Earth Sphere Federation, she left Marina's side to find a way to help her country. Later on, she became a member of Katharon.
- Lyle Dylandy - is a double agent, a spy of Katharon and Gundam Meister to Celestial Being.
- Eddie Miyasaka - is a space engineer and co-worker of Saji Crossroad, Eddie is actually a former worker of the Union army, but joined Katharon.
- Ikeda - is a correspondent for the Japan News Network (JNN) in season 1, and a member of the rebel group Katharon in season 2.
- Division Head Mahal - is a Section Chief for Katharon's base near Suihr.
- Sulu Suluzu - a female Innovade of the same base sequence type as Telicrya Herfi. Currently a member of Katharon.
- Hermiya - presumed to be an Innovade; unclear of her complete nature as her make is inspired by the A.I. holograms Hanayo and Hayana.
Katharon was created when the A-Laws began abusing their power to massacre innocents and force unallied nations to be assimilated into the Federation. Their main goal was to depose the government, but the A-Laws had them outmatch, both in technology and numbers.
After learning that Celestial Being had reappeared to fight the A-Laws, a new hope arose for Katharon. One of their contacts, Lyle Dylandy (the second Lockon Stratos), provided them with information on Celestial Being's raid on a Federation prison, during which Katharon members took advantage of the chaos to free other several prisoners.
Celestial Being by warding off the A-Laws during one of their attacks. Celestial Being brought fugitives Marina Ismail and Saji Crossroad to Katharon's Middle East base. After some introductions, Klaus Grad, an important member in the organization, tried to win over Celestial Being's support in overthrowing the Federation government; however, he was rejected, as Celestial Being's current objective is simply the annihilation of the A-Laws.
Earlier in the series, their meteor base, Lazerous, was destroyed by an A-Laws detachment. Later on, their Middle Eastern base is overrun by the A-Laws deployed automaton robots. The survivors evacuated to the base near Suille.
When the entire Suille capital was annihilated by Memento Mori, the Katharon leadership decided to dispatch their entire space fleet to destroy the superweapon. Unfortunately, the dominance the A-Laws have generally maintained over Katharon is made all the more apparent, as half of Katharon's second space fleet is destroyed by Momento Mori's upwards firing arc, and more than 93% of their missiles fired at the weapon are intercepted by the defensive fleet and a handful of mobile suits. The rest of the space fleet suffers heavy damage from the A-Laws defenders, losing most of their mobile suits to the A-Laws' own, and several ships to Innovator Healing Care. Only the intervention of Celestial Being did most of the fleet survived and the superweapon destroyed.
Katharon later received word from a number of Federation dissidents that they were planning a coup d'état to unseat the Federation government. Klaus was willing to accept their help, as they had few options left.
Soon enough the coup d'état faction seized control of the Advanced European Union's orbital elevator in Africa, planning on having the civilians witness the brutality of the A-Laws. Katharon assisted in the battle against the Federation loyalists. Unfortunately, the A-Laws fired at the elevator with a new Memento Mori, causing the elevator's superstructure to auto-purge its hull. Only the urging of Celestial Being made the combatants work together to protect the nearby cities from the fallout.
Nonetheless, the disaster allowed the Federation to grant the A-Laws total control of its regular army, enabling them to hunt down Katharon cells one by one. However, the general populace had been crying out for peace, due to the spread of a song Marina Ismail had composed with the orphans.
Katharon gathered its forces and headed into space, where the A-Laws were focusing all their attention on destroying Celestial Being. Working with the remnants of the coup d'état faction, they caught the A-Laws unaware taking full advantage of the anti-GN particle cloud which the A-Laws set up to nullify GN particle weapons. Then suddenly, a massive particle beam comes from the dark side of the moon, annihilating the A-Laws fleet and destroying one Katharon cruiser. The beam's source reveals itself as a massive colony ship, Celestial Being. Celestial Being declared that they would atone for their sins by retaking the supercomputer Veda from the true power behind the Federation and A-Laws—the Innovators. Nonetheless, Katharon and the coup d'état faction assisted them in the final battle.
When Veda was retaken, the A-Laws were officially disbanded and a new Federation reorganized. The members of Katharon ceased to be outlaws and helped govern the new Federation Government. Though former Katharon member Klaus Grad had promoted in the rank of the representative in United Federation's council of the political matters.
Two years after Katharon was disbanded, a movie titled Celestial Being depicted the anti-government group as the good guys attempting to stop the A-Laws, led by Alejandro Corner, from taking over the world.
Much of Katharon's fighting strength is mostly based on outdated mobile suits and carriers. Katharon's space fleet is composed primarily of modified Virginia-class cruisers and Laohu transport vessels. Their numbers add up to at least 23. However, during the assault on Memento Mori, the majority of the fleet was destroyed. At least two Virginia-class ships remains intact. The bulk of Katharon's forces are composed of obsolete mobile suits such as the MSER-04 Anf, MSJ-06II-A Tieren Ground Type, AEU-05/05 AEU Hellion Perpetuum, VMS-15 Union Realdo, SVMS-01 Union Flag, and AEU-09 AEU Enact. Many of Katharon's mobile suits have been repainted with a unique blue color scheme. On average, a single GN drive powered A-Laws mobile suit can utterly decimate an entire squad of Katharon's outdated mobile suits in combat. Overall, Katharon's forces are much weaker than the forces of the Earth Sphere Federation Army and A-Laws, which makes them easy targets, thus Katharon forces generally rely on Celestial Being and its Gundams to help win more battles. Despite their obvious tactical disadvantage, Katharon's conventional mobile suits can be a match for the ESF and A-LAWS' GN mobile suits if there was an anti-GN particle cloud which reduce the power of all GN particle weapons.
- Katharon vaguely resembles the Anti Earth Union Group (AEUG) and Karaba, both organizations which fought the corrupt Titans (which A-Laws resembles) in the U.C. timeline. The biggest difference is that while AEUG and Karaba had access to advanced mobile suits through Anaheim Electronics, Katharon had no such provider to fall back on, thus relying on obsolete mobile suits.