U.M.N., short for Unus Mundus Network (One World Network), is an informational network that spans the entire universe. Its non-locality is a large factor in its use in space warps and FTL (faster than light) communications. The U.M.N. Control Center is located on Second Miltia. This includes all facilities associated with the U.M.N. including the U.M.N. Transportation Gate management facility. The U.M.N. is under the jurisdiction of the U.M.N. Management Agency, meaning the U.M.N. Management Agency virtually controls all information within the Galaxy Federation, making it a very influential agency within the central government. The agency relies on Vector Industries to provide 98% of its facilities and resources. The Zohar-powered superweapon, Proto Ω, used the UMN as a weapon. Using a UMN Phase Transfer Cannon, Proto Ω could strike virtually any target in civilized space and completely obliterate it.

Certain points on the U.M.N. represented by actual points in space are known as Column Areas. These are specially designated areas of space normally marked by beacons where ships can gate in and gate out of hyperspace. A vessel must first interact with the U.M.N. in the Column Area, transmit a flight plan and a usage fee to the U.M.N. Transportation Gate management facility then receive clearance to gate into hyperspace. The space between recognized Column Areas is small on a galactic scale, but with the increasing number of Gnosis attacks on ships out in deep space the sometimes day-long layovers where ships have to travel in normal space between Column Areas can prove fatal. Such a fate befell the Federation cruiser Woglinde and her escort fleet from the 171st Marine Division. So far there has been only one known craft in the Xenosaga universe that is capable by-passing all known U.M.N. checkpoints and entering hyperspace without interacting with the U.M.N. That craft is the E.S. Dinah created by Vector industries for the KOS-MOS Project.

In Xenosaga: A Missing Year, it is explained that despite its widespread usage, no official data on the development or nature of the U.M.N. is recorded, and any details are kept solely by Vector.

Grimoire Verum, a scientist who worked for Vector on Lost Jerusalem and deciphered some of Lemegeton, existed for centuries in the U.M.N. A year prior to the events of Episode III, Shion and the anti-U.M.N. organization known as Scientia discovered that Grimoire was behind a recent wave of organized Gnosis attacks on human cities, which came to be known as Gnosis terrorism, and they put a stop to him. Grimoire had been using the U.M.N. to conduct these attacks in an attempt to find his daughter, Nephilim.

The U.M.N. was built upon the actual Unus Mundus, the human collective consciousness which had existed there long before the transfer columns and other U.M.N.-related technologies were developed. At the end of Episode III, all of the U.M.N. transfer columns disappear, restricting mankind to conventional means of travel. MOMO and the organization Scientia plan to develop a new network that would span the galaxy.

The symbol of the U.M.N. is a snake biting its own tail, also known as the Ouroboros.

The term unus mundus, literally "one world," was used by psychiatrist Carl Jung to describe a state beyond this world where every contradiction in physics, like synchronicity and the EPR Paradox, can be explained. A place where every relationship, such as that of the mind to mind, or mind to matter, can also make sense.