Proxima Centauri (or Alpha Centauri C) was a star in the Alpha Centauri system located less than 20 light years from Sol. This inhabited system was of the Alpha Quadrant. There was at least one planet that orbited Proxima Centauri. (Star Trek VI: The Undiscovered Country, production art; TNG: "The Naked Now", ENT: "Borderland")
In early 2154, Earth's Proxima colony reported Klingon warship in its vicinity. Admiral Maxwell Forrest believed that the Klingons were conducting reconnaissance scans for a future strike. (ENT: "Borderland")
Later that year, a Rigelian freighter departed Earth two hours after Doctor Phlox was abducted. According to a filed flight plan, the freighter's destination was Proxima colony. However, the trajectory of this freighter wouldn't take it anywhere near the colony. Upon coming to this conclusion, Captain Archer cancelled shore leave. Soon afterwards, his ship, the Enterprise, was in pursuit of the freighter. (ENT: "Affliction")
In the 24th century, Proxima Centauri was home to Starfleet's Proxima Maintenance Yards. Under the command of Admiral Drazman in 2371, Commander Benjamin Sisko, Doctor Julian Bashir and Lt. Jadzia Dax planned to visit the Yards in that year. (DS9: "Past Tense, Part I"). The Proxima colony was, also, home to the Proxima Centauri Interplanetary Bowling League. (TNG: "The Schizoid Man")
|Alpha Centauri system|
|Alpha Centauri A • Alpha Centauri B • Proxima Centauri|
|Centauri VII • Proxima colony|
Apparently in an early draft of TOS: "Wolf in the Fold", a Human colony established before 2156 was referenced as Alpha Proxima II, possibly intended as a planet in this system. The name was later replaced as Alpha Eridani II in the final episode. The Alpha Proxima II name however survived in such reference sources as Star Trek Maps, Star Trek Concordance and the entry on Startrek.com.
The location of Alpha Centauri (misspelled as "Alpha Centuri") identified in the "The Explored Galaxy" star chart placed it between the Tholian Assembly and Romulus. Both were identified in DS9: "Call to Arms" as being located in the Alpha Quadrant.
The chart naming stars within 20 light years of Sol was drawn by Rick Sternbach for the Star Trek Spaceflight Chronology in the late 1970s. Found on page 77, this chart showed Earth commercial and exploration routes after the use of warp drive began. There were no commercial or exploration routes to Alpha Centauri C. This chart would later appear in the episodes "The Last Outpost" and "Conspiracy".