Klingon space or Klingon territory was the territorial region of space claimed by the Klingon Empire.

In 2016, a Vulcan ship crossed into Klingon space near H'atoria and was immediately destroyed by the Klingons. (DIS: "The Vulcan Hello")

In 2152, the IKS Bortas tracked a refugee ship from the Klingon protectorate of Raatooras to a system just outside of Klingon territory, where they discovered that it had been rescued by the Human vessel Enterprise. Following an engagement between the two vessels, Enterprise Captain Jonathan Archer was put on trial on Narendra III, under the suspicion of conspiring against the Klingon Empire. While awaiting sentence, Archer was relying on Sub-commander T'Pol and Commander Charles Tucker III to get Enterprise safely out of Klingon territory whatever the outcome. Archer was sentenced to lifelong exile on Rura Penthe. As Enterprise was deep inside Klingon territory, T'Pol noted that an attempt to rescue the Captain was out of the question. However, she was able to recover Archer using diplomatic channels. (ENT: "Judgment")

The Tezra, a ship of the Tellarite Mining Consortium was seized by the Klingons after Captain Skalaar crossed into Klingon territory while hauling firesalt. As Skalaar recalled, he hoped to trim two or three days off his journey by cutting across the most insignificant corner of Klingon space, only to learn very quickly that there was no thing as an insignificant corner of Klingon space. To pay his impound fee, Skalaar become a bounty hunter. In March 2153, he captured Jonathan Archer, intending to deliver him to the Klingons. Following Archer's abduction, Enterprise learnt from Kago that he was halfway through Klingon space. Less than six light years from Klingon space, Enterprise set a course to search and ultimately recovered their captain. (ENT: "Bounty")

In May of 2154, a group of Augments crossed into Klingon space aboard a stolen Klingon Bird-of-Prey. Arik Soong suggested the Briar Patch as a hiding place once they were safely through Klingon space but his suggestion was rejected by Malik, the self-appointed leader of the Augments. Later, Enterprise used a Klingon warp signature and a universal translator programmed with seven Klingon language dialects to pass as a Klingon vessel within Klingon territory to intercept the Augments. (ENT: "The Augments")

Later that year, Enterprise set course for Klingon territory after Doctor Phlox was abducted. Captain Archer requested the assistance of Columbia in their search, noting in his starlog "We'll have a better chance of making it through Klingon territory with twice the firepower." (ENT: "Affliction", "Divergence")

In 2233 of the alternate reality, the USS Kelvin was on the edge of Klingon space when it was attacked by the Narada, a Romulan vessel from 2387 of the prime timeline. (Star Trek)

In 2256, during the Battle of the Binary Stars, T'Kuvma broadcast a message from his flagship on all subspace bands: "Members of the Federation. What you call your most remote borders, I call too close to Klingon territory." (DIS: "Battle at the Binary Stars")

Six months since the start of the war, the USS Discovery was running drills near Klingon space. Discovery was responsible for scuttling the USS Glenn, a sister ship which was adrift by Klingon territory. (DIS: "Context Is for Kings")

When Captain Gabriel Lorca was abducted in a shuttlecraft by a D7-class vessel, Acting captain Saru ordered Commander Airiam to inform Lieutenant Paul Stamets that Discovery may be making multiple spore jumps in rapid succession throughout Klingon space in an attempt to track Lorca's captors. Repeated use of the spore drive in attempts to rescue Lorca resulted in Ripper entering an extreme state of cryptobiosis and becoming unresponsive. Stamets resorted to injecting himself with a sample of tardigrade DNA and entering the spore chamber to act as the navigation computer. The jump was a success and Lorca was recovered, along with another Starfleet prisoner, Lieutenant Ash Tyler, with Discovery departing Klingon space. (DIS: "Choose Your Pain")

In 2259, Khan Noonien Singh took refuge in the Ketha Province on Qo'noS, knowing that for Starfleet to approach Klingon space would risk a war. After using a K'normian trading ship to recover Khan from Qo'noS against the orders of Admiral Alexander Marcus, Captain James T. Kirk found that a warp core malfunction had stranded his ship on the edge of Klingon space. As it transpired, Marcus had the Enterprise warp core sabotaged, intending for the Enterprise to use advanced long-range torpedos against Khan on Qo'noS. The plan was for the Klingons to discover the Enterprise and in response to the torpedo attack, start a war with the Federation. Thankfully, Pavel Chekov was able to repair the warp drive, allowing the Enterprise to return to Federation space. (Star Trek Into Darkness)

In 2293, the USS Enterprise-A entered Klingon space, masquerading as the freighter Ursva, to rescue Captain James T. Kirk and Doctor Leonard McCoy from Rura Penthe. Meanwhile, Captain Hikaru Sulu ordered the USS Excelsior on an aborted raid into Klingon territory from Sector 21185 on an ill-advised rescue attempt. Sulu, who attempted to sneak the Excelsior into Klingon territory by traversing the Azure Nebula at maximum warp, was discovered by a Klingon battle cruiser commanded by Kang. While Sulu explained that the Excelsior was on a survey mission, studying the nebula, and had gotten lost due to a malfunction in the navigation system, Kang offered to escort the Excelsior back to Federation space. As the Excelsior emerged, she fired a modulated positron beam that triggered a thermochemical reaction, and successfully disabled Kang's ship. The Excelsior then made a break for Qo'noS, but was almost immediately intercepted by three Klingon battle cruisers. The Excelsior and Klingon ships continued to exchange fire until the Excelsior was forced to retreat back to Federation space. (Star Trek VI: The Undiscovered Country; VOY: "Flashback")

Following the outbreak of civil war in the Empire in late 2367, Captain Jean-Luc Picard of the USS Enterprise-D led a Federation fleet into Klingon territory in order to prevent Romulan forces from covertly supplying the House of Duras. Though Commander Sela noted that Romulan vessels could slip through Klingon territory at will via cloak, Picard employed a tachyon detection grid to detect them. (TNG: "Redemption II")

In 2369, the Enterprise found Relay Station 47 abandoned, with evidence suggesting that encrypted messages sent from there had been tampered with. As the station was close to Klingon space, the Klingons came under suspicion in connection to the disappearance of the crew. (TNG: "Aquiel")

In 2372, during the Klingon-Cardassian War, the Pentath system bordered Klingon territory. When an outbreak of Rudellian plague struck the Cardassian colony on Pentath III, the Cardassians feared raids and so requested protection from Starfleet for their convoys of medical supplies and relief workers. (DS9: "Rules of Engagement")

In 2373, a memory virus that Lieutenant Commander Tuvok had contracted aboard the Excelsior eighty years earlier led him to advise extreme caution when close to Klingon space. Now aboard the USS Voyager, Tuvok was reminded by Lieutenant B'Elanna Torres that the Klingon Empire was on the other side of the galaxy. (VOY: "Flashback")

During the Federation-Klingon War, Starfleet sent an infiltration team to Klingon territory in order to prove that Klingon Chancellor Gowron was a shapeshifter. This team consisted of Captain Benjamin Sisko, Lieutenant Commander Worf, Constable Odo and Chief Miles O'Brien. Their mission was complicated when they learnt from Starfleet Intelligence that Gowron had relocated Klingon military headquarters to Ty'Gokor. Located in an asteroid field deep in Klingon space, Ty'Gokor was considered the heavily fortified installation in the Empire. (DS9: "Apocalypse Rising")

In an unknown, future timeframe, the USS Pasteur crossed the border into Klingon territory to scan the Devron system for a temporal anomaly. (TNG: "All Good Things...")

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