Sector 31
Sector 31 was a region of space in the Beta Quadrant. A segment of the Romulan Neutral Zone was located in this sector. 

In 2364, communication with Federation starbases in this sector ceased as of stardate 41903.2. The identity of the assailant that had destroyed the bases was unknown at the time. () It was later on determined that the Borg were responsible for the attack. ()

In the alternate 2259, this sector was labeled on a map of the Alpha Quadrant. This map was in a collection of graphics and video media that were seen on a powerwall in the offices of Admirals  and  at Starfleet Headquarters. ()

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Sector 0031
Locations (alternate reality)