The Trans-Hydian, unofficially known as the Borderlands, was an area of the galaxy "north" of the Perlemian Trade Route. Home to worlds with long heritages and lineages, the area originally did not experience economic development as The Slice and the Trailing Sectors had. It was burdened with geographic anomalies such as the Radama Void and a constant threat of Mandalorian and Sith invasions, if only by sheer rumor and fear. As the Hydian Way expanded, economic development came. Some worlds, such as Ord Mantell, were established in this area in an effort to protect settlers and investors from various threats. During the Galactic Civil War, the area became known as the "Borderlands" due to its split loyalties between the Alliance to Restore the Republic and the remaining Galactic Empire.
This region was a militarized zone incorporating, among others, the Listehol Run, the Abregado, Breago and Obroa-skai systems, Elom, Jendorn, and Hettsk. Though not an official region or sector of the galaxy, the Borderland Regions comprised remaining Civil War battle zones.
In 10 ABY, prior to the Battle of Calamari during Operation Shadow Hand, the New Republic received word that fringe worlds in these regions had been attacked by monstrous vehicles called "city-smashers" by the survivors. Planet surfaces had been burned away, and it was later revealed that this had been nothing more than a test of the Empire's new superweapons, the World Devastators.
- Star Wars: The Clone Wars – "Ambush" (Appears in flashback(s))
- Star Wars: The Clone Wars – "Rising Malevolence"
- Star Wars: The Clone Wars – "Jedi Crash" (Appears in flashback(s))
- Star Wars: Empire at War: Forces of Corruption (Mentioned only)
- "Mission to Zila"—Star Wars Adventure Journal 3 (Mentioned only)
- (As "Borderland Region")
- (As "Borderland Region") (Reprint)
- Heir to the Empire (First appearance)
- (Mentioned only)
- "Retreat from Coruscant"—Star Wars Adventure Journal 5
- Shield of Lies (Mentioned only)
- Heir to the Empire Sourcebook
- Star Wars: The Roleplaying Game, Second Edition
- Dark Force Rising Sourcebook
- Wanted by Cracken
- Dark Empire Sourcebook
- The Last Command Sourcebook
- The Thrawn Trilogy Sourcebook
- Star Wars Adventure Journal 10
- The Complete Star Wars Encyclopedia
- The Essential Atlas (As Trans-Hydian)
- The Essential Guide to Warfare
- Strongholds of Resistance