In the Universal Century timeline, space colonies are placed at five gravitationally stable points in space, known as Lagrangian points. In most cases, a Lagrangian Point is home to more than one group of space colonies. A group of colonies that occupy a Lagrangian Point are known collectively as a "Side". Because Sides sometimes share a single Lagrangian Point, it is possible to have two Sides in close orbit to one another. All colonies in the Universal Century are O'Neill "Island 3" type colony cylinders.
Side 1 is located at Lagrangian point 5 (L5), and is called Zahn. This side serves as the Earth Federation's space capital. This side was also one of the first colonial Side the Principality of Zeon attacked during the One Year War. Side 1 is home to several colonies, among them Shangri-La, Londenion, Colony 30, Island Blade, Island Ease, and the Pia Albanian colony.
Side 2 is called Hatte, and is located at L4. This was one of the first Sides attacked by the Zeon during the One Year War. Island Iffish, the colony that was dropped during Operation British, was taken from Side 2. Later, this Side adopted the name Zanscare Empire. Side 2 is home to Amelia, Macedonia, Blue 3, Calabria, Heras, Island Iffish, Colony 13, the 18th Block, and the 21st Block.
Side 3 is located behind the moon, at L2, and is known as Munzo. Side 3 was the only Side to never use the "open-type" colonies. They instead used "closed-type" colonies, which removed the glass "sky" panels and was a completely "solid" cylinder with no open view to space. This allowed each colony to house greater capacities of people.
In U.C. 0052, Zeon Zum Deikun moved to Side 3 and began to spread his philosophy of Contolism - essentially that the earth was sacred, and that human beings had a solemn right to protect it. This philosophy also encouraged the people of the space colonies to consider themselves independent from earth. In U.C. 0058, under the guidance of Zeon Zum Deikun, Side 3 declared independence from the Earth Federation and formed as a republic. In U.C. 0068, Deikun died under mysterious circumstances, and Degwin Zabi took control.
Under Degwin's leadership, Side 3 became a dictatorship, and the National Guard regiments Side 3 maintained became a full fledged army. Degwin then announced the formation of the Principality of Zeon, setting himself up as the ruler and giving his four children unilateral control of the military forces. Simultaneous with this announcement came severe purges of the remaining followers of Zeon Zum Deikun living in Side 3. The Principality of Zeon began to mass-produce various warships and mobile suits in anticipation of an armed conflict with the Federation.
After the One Year War Side 3 came under the control of Prime Minister Darcia Bakharov, who pursued peace. Bakharov and the Federation reached an agreement whereby the Principality of Zeon would surrender, and Side 3 would be allowed to maintain its independence under the name "Republic of Zeon". The deal also allowed the Republic to maintain an armed force which would be subject to periodic inspections by the Federation. Although the agreement formally ended the war many Principality supporters rejected the offer, and chose instead to go into hiding.
Side 3 received additional space colonies in 0082 and again in 0083 as part of the Colony Reclamation Project, which sought to ease the overcrowding of Side 3. Side 3 remained the Republic of Zeon until they rejoined the Federation in U.C. 0100. Other colonies in Side 3 are Tigerbaum, Bieutar and Achilles.
Side 4 is known as Moore (sometimes spelt as Mua) and was located at L5. During the reorganization of Sides in U.C. 0084, Side 4 was moved to L1. Side 4 was one of the first colonies attacked by the Zeon during the One Year War. Moore is the location of the Thunderbolt Sector, a shoal zone created from the debris of mobile suits, ships and some of the destroyed colonies themselves. Some experts have suggested that the colony used for Operation British originated here. Side 4 was eventually reconstructed into the Frontier Side in Mobile Suit Gundam F91. Other known colonies in Side 4 are New Manhattan, which was the headquarters of the Illuminati resistance group in G-Saviour, and Industrial 7, a closed-type industrial colony managed by Anaheim Electronics.
Side 5 is known as Loum, and was located at L1. During the reorganization of the Sides in U.C. 0084, Side 5 was moved to L4. During the One Year War, this Side became a battle zone when the Principality of Zeon attempted to capture a colony from Side 5 to drop on the earth. When the Earth Federal Space Force intercepted the Zeon, a massive battle for Side 5, later called the Battle of Loum, erupted between the two forces. At the end of the One Year War this area became known as the shoal zone.
Side 6 is known as Riah, and is located at L4. Side 6 declared independence from the Earth Federation on April U.C. 0077, and thanks to backing from the Principality of Zeon, succeeded in gaining independence, at which point this Side adopts the name Riah Republic. Unlike Side 3, which went to war to claim total independence from the Earth Federation, Side 6 maintained diplomatic ties with the Federation, and left the Earth Federation on good terms. Side 6 declared neutrality in the opening weeks of the One Year War, and managed to avoid most of the conflict; however, the Federation maintained a secret R&D base there, and Side 6 was targeted by the Zeon after it was discovered. This story is told in Mobile Suit Gundam 0080: War in the Pocket.
Side 6 would later rejoin the Earth Federation. During the reorganization of Sides in U.C. 0084, Side 6 was moved to L5.
Many colonies are known to be located in Side 6: Ribo, Baldur Bay, Franchesca, Ontario, Ukraine, Kamiigusa, Palda, Morudeigan and New Madera.
Side 7 is known as Noa, and is located at L3. At the time of its introduction in the original Mobile Suit Gundam, Side 7 consisted of a single, incomplete space colony that housed a Federation R&D base involved with the Vinson Plan. This Side became famous in September of U.C. 0079, when the assault carrier White Base and its Mobile Suits successfully fended off an attack by Zeon Mobile Suit pilots, and in doing so marked the first battle between Zeon and Federation MS inside a colony. After the war, this Side 7 colony is completed and given the name Green Noa 1. The side itself was renamed Green Oasis. A second colony, known as Green Noa 2 (codenamed "Gryps" by the Titans), is added to the cluster in U.C. 0085. There are two known colonies in Side 7: Green Noa and Gryps/Gryps II.
Side 8 is a late addition to the Universal Century timeline. The colonies, now referred to as "Settlements" are primarily focused on agriculture and are located at L1. One such Settlement is known as "Gaea". The leader of Gaea is Councilor Graves.
- Moon Moon: A lost "Island 1" type colony, home to a primitive group of space dwellers. Seen in Mobile Suit Gundam ZZ and Mobile Suit Moon Gundam.
- Sweetwater: It was created through the combination of an Island 3 "open-type" colony with a "closed-type" colony as a place for refugees of the One Year War, Gryps Conflict, and First Neo Zeon War. In U.C. 0093, Neo Zeon, now led by Char Aznable, used the colony as a base from which they could launch another war against the Earth Federation. Due to Aznable's popularity among the colonists, Neo-Zeon's existence was hidden from the inspections conducted by the task force Londo Bell until the commencement of the Second Neo Zeon War.
- Laplace: A Stanford Torus-type colony, used as the official residence for the prime minister of the Earth Federation. Destroyed in U.C. 0001.