|Dominant species:||Terran, Bajoran, Vulcan, Andorian, Tellarite, others|
|Location:||Alpha and Beta Quadrants|
|System of government:||Democratic republic|
|Head of state:|| Chairman|
In the mirror universe, the Galactic Commonwealth was an organization founded in the year 2378 that replaced the Terran Rebellion following the establishment of the Tripartite Armistice with the Klingon-Cardassian Alliance and the end of decades of enslavement. The Commonwealth consisted of more than two dozen worlds in a twenty light year span from Sol and was surrounded by a ten lightyear wide neutral zone that blocked Alliance vessels access to Commonwealth worlds. One of its first allies was the Romulan Star Empire, which the Rebellion had also helped to return to power.
A descendant of the Terran Empire, the Commonwealth was heavily influenced by the efforts of Spock and the Memory Omega project that he instituted. The Commonwealth focused on promoting the common good for all races and strived to avoid returning to the imperialistic ways of its past. It launched multiple social programs and conducted missions to repair the damage that had been caused to multiple worlds by both the Alliance and the Empire that came before it. The Commonwealth also employed a naval force that consisted of several vessels including the Defiant, the Intrepid, the second Intrepid, the Courageous and the Enterprise, with the Enterprise as the flagship.
Headquartered from the planet Deneva, the Commonwealth was headed by a chairman and overseen by the Commonwealth Assembly. It consisted of Terrans, Andorians, Tellarites, Vulcans and several other races. As of 2381 the Chairman of the Commonwealth is Michael Eddington.
In the armistice, more than two dozen worlds were formally ceded to the Commonwealth in a 20 lightyear zone around Sol. The entire territory was surrounded by the Terran Neutral Zone, 10 ly thick. The Commonwealth was intend on peaceful expansion by voluntary admission of worlds. Its territory shared borders with the Klingon Empire, Cardassian Union, Romulan Star Empire and the Taurus Pact.