The Unknown Regions, Unknown Space, Unknown Sector, or Unknown Territories was the collective term for all regions of the galaxy not formally charted; it differed from Wild Space in that Wild Space was usually minimally charted, but not fully explored.
The Unknown Regions could be broadly defined as areas not connected with the skein of reliable or well-known hyperspace routes spanning the galaxy, did not look to Coruscant as the ultimate center of civilization, or were not under the broad hegemony of the Galactic Republic before the Galactic Civil War—but the full reasons behind this lack of contact remain unknown. At the region’s outer edge, was the Hyperspace disturbance at the edge of the galaxy, in locations such as the Crispin system that gazed out at the Intergalactic Void.
The reach of civilization extended at least nominally to the edge of the Galactic disk—for instance, the territory of the Corporate Sector extended to the end of the Tingel Arm. The galactic disk and some satellite galaxies were mapped well enough that the omission of thirty-seven systems (including Kamino) from stellar charts were obvious gravitational anomalies, even when scanning from afar.
The large galactic volume designated as the "Unknown Regions" included uncharted areas in dense nebulae, globular clusters, and the galactic halo. 15% of the galaxy's volume was contained within the Unknown Regions. Many governments repeatedly sent scouts into the Unknown Regions. General Wedge Antilles once remarked that "If you continue to map the Unknown Regions, you'll have to call them something else."
The Unknown Regions approached nearest to the galactic disk behind Bakura, Bilbringi, and the Imperial Remnant. Important powers in this area of space included the Chiss Ascendancy, the Ssi-ruuvi Imperium, the Vagaari, the Killik Colony, and the Empire of the Hand, but it was also home to species such as the Croke, the Ebruchi, the Nagai, the Tofs, and the Eickarie.
One hypothesis by a noted scientist suggested that a mass of dark matter intersected the galaxy in this region, creating gravitational anomalies that hindered navigation. However, the lack of any tidal disruption of the galaxy's spiral form (as shown in Jedi Archives) may disprove this supposed dark mass. It is clear, moreover, that much of the Unknown Regions were passable to determined travelers—for instance, Corellian traders had been in contact with the Chiss for many years before their "discovery".
Chiss Grand Admiral Thrawn, a native of these parts, was dispatched aboard the Imperial-class Star Destroyer Admonitor to the Unknown Regions during the years of the Galactic Civil War, ostensibly on a simple mapping expedition, but in reality to explore and subjugate entire sectors for the Galactic Empire. While there, Thrawn seems to have encountered the Yuuzhan Vong [though the Yuuzhan Vong were from another galaxy]. He also created a shadow Empire, the Empire of the Hand.
Due to the very fact that the region was "unknown," it presumably had not been charted and divided into sectors.
The depiction of the Unknown Regions varies from source to source. Some fans would like to limit the term to areas outside the plane of the galactic disk, and this hypothesis is not contradicted by any canon or EU evidence. It is supported by movie canon, which describes a Galactic Empire, and in which the entire galaxy can be surveyed for any lost planet, fugitive, or Rebel base.
In Vision of the Future, the space known to the Old Republic, Empire, and New Republic is not specifically assigned to any section of the galactic disk, nor are the Unknown Regions. They do appear adjacent on the map, which includes the disk. The territory under the hegemony of the Empire of the Hand, while by no means comprising all of the Unknown Region, seemingly embraces as much as 240 sectors, roughly a quarter of the volume of known space. Although huge, this volume is emptier than the Galactic disk, since the combined total of the Unknown Regions contains no more than one percent of the galaxy's stars.
In contrast, The Essential Chronology and New Jedi Order series, as well as the associated galactic map, have bulked the Unknown Regions on one side of the Galactic disk, and this seems now to be a geometric projection of sub-volumes above the disk. However, it should be noted that most fans subscribe to a two-dimensional interpretation, in which the Regions actually touch much of the disk. Worlds such as Kamino, lying "beyond the Outer Rim" on the opposite side of the galaxy, in a dwarf satellite galaxy 70,000 light years from the galactic center, might also be considered as lying on the edge of this zone.
At the end of Star Wars: Knights of the Old Republic II: The Sith Lords, the Jedi Exile goes out to the Unknown Regions of the galaxy to search for Revan who at the time is searching for the mysterious True Sith.
The Unknown Regions, also known as Gyaros to the Chiss Ascendancy or Ancile Regnum to the Sith, was a massive region in the "north" of the the galaxy, that had been left largely unexplored by all the galaxy's major powers up until the late 60's ABY.
Despite its seclusion from the greater galaxy, the Unknown Regions was home to several major galactic powers. The most well known of these was the Chiss Ascendancy, which maintained a minimal relationship with each of the major galactic powers, but refrained from becoming fully involved with them, preferring to keep to their own affairs. Both the Galactic Empire and New Republic had allocated great amounts of funding for the exploration, but little information could be afforded from the blackness of the Unknown Regions.
This gap in the archives of the Galactic Senate meant that several powers could continue to grow and strengthen without the inevitable interference that negotiations with them would cause. One such power was the Sith Order of Decreto.
The Sith Order of Decreto, although originally from a part of the galaxy known the the Galactic Republic et al, had made there way into the Unknown Regions in the year 5,000 BBY and remained their for many thousands of years. They quickly hid themselves away from even those who were their neighbors, becoming so deeply secretive (but influential) that they could direct the affairs of the galaxy without anybody knowing anything about them.
After many years of seclusion (not including the occasional encounters) the Sith Order of Decreto under the direction of their Emperor Darth Abeonis (a former Jedi) revealed themselves to the galaxy in the form of an invasion of the Chiss Ascendancy. In the years that followed, the Unknown Regions were opened up much more than they had been previously; with travel within the Sith Order of Decreto relatively easy, the black market expanded into the Unknown Regions. It was this market that allowed for the Jedi Cerras Ki to survive during his seven year journey, and to procure his weapons.
Long after the end of the Unity era and deep into the Dark Age the Unknown Regions were eventually opened up, to a certain degree, and become largely known to the peoples of the galaxy, although great swathes remained hidden away on the orders of the Sith Council. By the mid Dark Ages, almost the entire region had been explored, but, as the last part of the galaxy that was explored, the various map-makers decided to keep the name Unknown Regions, for symbolic reasons.
During this time, a good amount of the Unknown Regions to the "north" of the galactic Core was controlled by the Vancita Alliance.