"Only Qo'noS endures".
Qo'noS (transliterated to Kronos in English) was a planet in the Klingon planetary system. This system was located in the Alpha Quadrant. This inhabited Class M planet was the homeworld for a warp capable species, the Klingons, and was the capital of the Klingon Empire.
- Main article: Klingon history
In 2293, the Klingon moon of Praxis, a key energy-production facility for the Klingon Empire, exploded after an accident involving over-mining which sent out a subspace shock wave, causing severe damage to the planet's ozone layer. This event forced planning for the evacuation of the planet and led to the signing of the First Khitomer Accord with the Federation. (Star Trek VI: The Undiscovered Country)
- Caves of No'Mat
- Hamar Mountains
- Sea of Gatan
- Kang's Summit
- Kri'stak volcano
- Lake of Lusor
- Skral River
- Glob fly
- Grint hound
- Grishnar cat
- Jackal mastiff
- Monster dog
- Kolar beast
- Saber bear
- Serpent worm
The Klingon homeworld was unnamed until Star Trek VI: The Undiscovered Country, in which it was identified as Kronos (spelled that way in the film's script). The spelling "Qo'noS" was subsequently devised by Marc Okrand, in order to conform to his previously developed rules of Klingon orthography.
Other unofficial names for the Klingon homeworld exist. Kling came from an abandoned premise which was mentioned in TNG: "Heart of Glory" and a few FASA role-playing games. It was also used (along with Klinzhai) in the 1989 edition of The Worlds of the Federation and, along with the other accepted names for the homeworld, in the Star Trek: Star Charts (page 56); in the Star Trek Encyclopedia, it was stated that Kling was in fact the original name for the planet but most people thought it was silly. Kling was now more commonly considered a major province on the planet Qo'noS. Klinzhai was another commonly-mentioned non-canon name; it was used mostly in the FASA RPG and various novels, as well as in the Star Trek: Starfleet Command video game series, until the release of Star Trek VI: The Undiscovered Country.
Location of Qo'noS
The common assumption among the fans and some of the production staff was that Qo'noS was located in the Beta Quadrant. The Klingon Empire bordered the Romulan Star Empire and the United Federation of Planets. The Ferengi and Cardassians were located on the other side of the Federation, and were thus located far from this Empire, This belief was made canonical with a display graphic from Star Trek: Insurrection that depicted the location of the Romulan Star Empire.  .
However, an examination of the dialog painted a different picture. The picture began to be drawn by the series Star Trek: The Next Generation. In "A Matter Of Honor", the Klingons and the Romulans had a series of skirmishes along their border. One of the battles was fought at Tranome Sar. In the "Reunion", K'Ehleyr stated that Klingon wars are rarely confined to the Empire. These wars had a tendency to spread to the neighboring star systems, than the Tholians and the Ferengi. The Tholians and Ferengi were both Alpha Quadrant species.
The sister series Star Trek: Deep Space Nine confirmed what had been already stated and added onto it. In "The Die is Cast", the Dominion identified the Klingons as a threat originating in the Alpha Quadrant. In "The Way of the Warrior", the Klingon Empire launched an attack against the Cardassian Union. They did this for the best interest of the Alpha Quadrant. It was revealed in this episode that relations between the two great powers have been for the most part amicable, save for the Betreka Nebula Incident. This was the first time that it was implied that these two great powers shared a border. In "Blaze of Glory", Captain Benjamin Sisko and Martok were discussing the ramifications of Human terrorists killing millions of Cardassian citizens. They agreed that the Cardassian allies, the Dominion, would retaliate not only against the Federation, but against the Klingons and the entire Alpha Quadrant. In "In the Pale Moonlight", it was revealed that the Dominion forces were crossing the Cardassian-Romulan border and were launching attacks against Federation ships. The Dominion was secretly planning to invade Romulan space from Cardassia, and, by their estimation, the Romulans would be defeated in three weeks. When Sisko was attempting to persuade Senator Vreenak to consider having the Romulans join the offensive against the Dominion, the Starfleet officer said: 'I'd pick the side most likely to leave us in peace when the dust settles. Maybe you're right. Maybe the Dominion will win in the end. Then the Founders will control what we now call Cardassia, the Klingon Empire and the Federation. So, instead of facing three separate opponents with three separate agendas, you'll find yourselves facing the same opponent on every side. There's a word for that. Surrounded. In the "Tears of the Prophets", Sisko stated that the three great powers that haven't allied themselves or had turned against the Dominion -the Humans, the Klingons, and the Romulans - have one goal: to drive this Gamma Quadrant power out of the Alpha Quadrant. In "When It Rains...", the Chancellor Gowron envisioned the Klingon Empire as the saviors of the Alpha Quadrant if they could drive the Dominion out of the quadrant.
This association of Qo'noS with the Alpha Quadrant was carried over to the sister series, Star Trek: Voyager. In "Faces", Chief Engineer B'Elanna Torres boasted that Klingon females were renowned in the Alpha Quadrant for their physical prowess and voracious sexual appetites. In "Flashback", Captain Kathryn Janeway reminisced about what it would be like to live in Captain James T. Kirk's era. In his era, large swaths of the Alpha Quadrant were yet to be explored, and Humans were on the verge of war with the Klingons. In "Flesh and Blood", Chakotay identified the Klingon bat'leth as an Alpha Quadrant weapon.
And finally, Qo'noS was mentioned as being located four days from Earth at warp 4.5 in the Enterprise episode "Broken Bow". Their homeworld cannot be farther away than 90 light years, as Archer referred to Risa in ENT: "Two Days and Two Nights" as being the farthest away from Earth any Human had gone to that point.
In conclusion, the Klingons were an Alpha Quadrant species. Their homeworld was located within 90 light years of Earth. The territory of their empire shared borders with the Cardassians, the Federation, and the Romulans. The Tholians and the Ferengi didn't share a border with the Klingons, but, nonetheless, they were influenced by events in the Empire.
- Qo'noS (Kronos, Kling): This planet was located in the Qo'noS system. The capital city for the uniglobal government and for the Klingon Empire was First City. The dominant species were the Klingons. Points on interest on this world were the Great Hall, Qam-Chee, Tong Vey, Quin'lat, Temple of G'boj, Kri'stak volcano, Lake of Lusor, and Caves of Kahless. The Klingons were warp capable in 930 A.D. On April 4, 24, 2151, the Enterprise, on its maiden voyage, visited this planet. This planet was on the front line during the brief Klingon Civil War of 2368. In 2378, there were counted 3.84 billion Klingons on this planet. (pg. 55, 61, 62)
- Qo'noS System (Kronos System, Kling System): This planetary system was located in the Qo'noS Sector. This was a single star system. Qo'noS was a K-class star with a magnitude of +3, which was ten times brighter than Sol. In 2293, the USS Enterprise-A visited this system. (pg. 56, 62)
- Qo'noS Sector: This sector was located adjacent to the Archanis Sector. (pg. 62)