Multiple realities
(covers information from several alternate timelines)
For the rouge Federation agency, please see Section 31.

Sector 31 was a region of space. 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. (TNG: "The Neutral Zone") It was later on determined that the Borg were responsible for the attack. (TNG: "Q Who")

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 Christopher Pike and Alexander Marcus at Starfleet Headquarters. (Star Trek Into Darkness)

As the result of the two-dimensional nature of the map, it is not possible to know the region's location in relation to the Klingon Empire. The map is visible in the video "Star Trek: Into Darkness" – User Interface VFX at [1]
According to Star Trek: Star Charts (p. 66), Sector 31, also known as the Glintara sector, was located in the Beta Quadrant.
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