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The first well-documented crossover into the mirror universe, in 2267

The mirror universe is a parallel universe where the patterns of events move in similar manners to that of the primary universe, but the intentions and characterizations are different, often showing "evil" characteristics in place of "good" and vice versa. Starfleet Intelligence, by 2267, referred to this reality as "Terran Empire parallel." The mirror universe shares a similar history to that of the primary universe and many of the same people exist in this reality, but they and the galaxy they live in are skewed versions of their "normal" counterparts. (Star Trek Adventures module: Core Rulebook)

Widely recorded as first being visited by James T. Kirk and several officers from the USS Enterprise in 2267, though in reality already encountered by the USS Discovery around a decade earlier. This parallel universe coexisted with the prime universe in the same space, but on another dimensional plane.

Because of the development of the mirror universe in canon and non-canon works over the years, several alternate mirror universes have been established. The page approaches the mirror universe from its most recent and complete canon-version with compliant non-canon works, accepting variations of the mirror universe presented in other non-canon works as alternate mirror universes.

Scientific research has suggested that there are several mirror universes. Such as the alternate mirror universe that Starfleet Captain Kira visited in 2383 and in 2384 with a Terran Emipre that was not destroyed by the Klingon-Cardassian Alliance.

The mirror universe was so named because most places, ships, and people that existed in the prime universe also existed there, although usually bearing the antithesis of many of their personal characteristics, in particular swapping their morally good characteristics (for example: altruism, kindness) for morally bad characteristics (for example: selfishness, cruelty) or vice versa, thus "mirror"-like. (DIS episode: "Despite Yourself"; ENT episode: "In a Mirror, Darkly"; TOS episode: "Mirror, Mirror")

By 2257, the Terran Empire and the United Federation of Planets were aware of the existence of their respective opposite universe, and both chose to classify that information to prevent deliberate crossovers; the Federation was fighting a costly war at the time they learned of the mirror universe and Starfleet admiralty was afraid of desperate attempts to reunite with loved ones, and the fascistic Terrans feared Federation ideals would inspire rebellion. (DIS episodes: "Vaulting Ambition", "The War Without, The War Within")

By the year 3189 the mirror universe had diverged from the prime universe enough that no reported crossings had occurred in the preceding 500 years. (DIS episode: "Die Trying")


Early history[]

It is not clear if the mirror universe diverged from the primary universe at some point or always existed in tandem, mirroring events and peoples. If the two universes did diverge it was at a point many hundreds of years ago. Phlox noted that the "great works" of literature in both universes were roughly the same except that the regular universe characters were "weak and compassionate," with the exception of Shakespeare. (ENT episode: "In a Mirror, Darkly")

In the mirror universe of Dark Mirror, Earth's history took a darker turn starting with the end of Homer's Iliad, where Achilles kills King Priam, instead of showing one moment of humanity. Khan Noonien Singh and the other supermen won the Eugenics Wars, but then wiped each other out. The Vulcans were also militaristic, as there was no Surak.

The mirror Klingons culture has a basis of celebrating the victory of Molor over Kahless. (ST novel: Dark Passions)

In the mirror universe, first contact was slightly different

On 5 April 2063, first contact between Vulcans and Terrans took place much as it did in the primary universe. However, once the Vulcans landed, instead of welcoming them with open arms, Zefram Cochrane shot the first Vulcan to step onto Terran soil and the Terrans proceeded to raid the Vulcan ship, the T'Plana-Hath. The gun used by Cochrane later would come into the possession of Commander Jonathan Archer, who wondered what would have happened had Cochrane not "turned the tables on [the Vulcans'] invasion force." With advanced Vulcan technology now at their disposal, the Terrans were able to expand the Terran Empire and conquer other worlds, including Vulcan. (ENT episode: "In a Mirror, Darkly")

It is not clear when the Empire began. Archer once stated that the Empire had existed for "centuries" as of 2155. Archer did not mention how many centuries, but by his statement, the Empire can be traced back to at least 1955, suggesting that it was a Terran political unit before it became an interstellar empire. The credits sequence for In a Mirror, Darkly used footage of battles going back at least to the "Age of Sail." It also appears that it is the empire that conflicts with the Xindi.
In the Mirror Universe Trilogy First Contact was the point of divergence with the primary universe; at this point, Zefram Cochrane warned the Vulcans about the Borg. Humans and Vulcans formed a militaristic alliance to wipe out the Borg, after which they became the Empire.
The Mirror Universe Saga had the Empire come about because the Romulans conquered Earth and enslaved humans for almost a decade. When Earth overthrew the Romulans it embarked on a program of conquest itself and became the Terran Empire.

The Bajorans and Trill had empires until they were conquered by Earth. (ST novel: Dark Passions)

The history of Ireland followed a similar course to its primary universe counterpart with respect to the country's numerous conflicts with Great Britain over the course of several centuries.

Hundreds of years prior to the 24th century, Kai Dava Nikende foresaw the conquest of Bajor by the Terran Empire in 2255 and the suppression of the Bajoran religion, which involved the killing of its priests, and the destruction of its icons such as the Orbs of the Prophets. Consequently, he preserved a fragment, known as a paghvaram, from each of them. During his orb experience with the Orb of Souls, he made contact with his primary universe counterpart, who was likewise the Kai of Bajor, and one of the fragments was transported to that universe for safekeeping. This may have been the first direct contact between the two universes. The paghvaram was kept in the village of Sidau in Hedrikspool Province, until it was stolen by Iliana Ghemor in 2376. (DS9 novel: The Soul Key)

22nd century[]

By the 22nd century with advanced Vulcan technology at their disposal, the Terran Empire had expanded and conquered other races, including the Vulcans, Andorians, Tellarites, Orions and Denobulans. In 2155, the ISS Enterprise, under the command of Captain Maximilian Forrest was the flagship of the Terran Empire's Starfleet. In January of that year, Commander Jonathan Archer mutinied against Forrest in order to take the ship into Tholian space to capture the primary universe starship USS Defiant which the Tholians had obtained. While the mutiny was ultimately unsuccessful, Captain Forrest had no choice but to continue the mission, since the ship's helm had been locked on auto-pilot.

Hoshi Sato declaring herself Empress

The Enterprise was later destroyed by Tholian ships, but not before Archer was able to take control of the Defiant. Archer tried to use the Defiant in a grab for power, intending to replace the Emperor, but was betrayed and killed by Hoshi Sato, who declared herself Empress. (ENT episode: "In a Mirror, Darkly"; ENT novel: Age of the Empress)

23rd century[]

In possession of the USS Defiant, the mirror universe was generally unaware of the primary universe. Knowledge of the primary universe and the Federation was restricted to the highest levels of the Terran Empire. In the primary universe, Section 31 had some knowledge of the mirror universe. (ENT episode: "In a Mirror, Darkly"; DIS episode: "Vaulting Ambition"; ENT novel: The Good That Men Do)

Symbol of the Terran Empire in the 2250s

In 2256, the USS Discovery inadvertently traveled to the mirror universe via the Mycelial network. During this time, the Empire was at war with several rebel factions of Vulcans, Andorians and other aliens. Also, the ISS Buran's captain, Gabriel Lorca attempted a coup against the Terran Empire's Emperor Philippa Georgiou. The ISS Shenzhou under Captain Michael Burnham hunted Lorca down until both Lorca and Burnham were presumed dead. (DIS episodes: "Into the Forest I Go", "Despite Yourself")

However it was not until 2267 that any official contact between the universes is recorded. By this time, the Terran Empire was the dominant power in the Alpha Quadrant. In a transporter accident caused by interference from an ion storm, a landing party from the USS Enterprise switched places with an identical party from the ISS Enterprise in the mirror universe. The four Starfleet officers – Captain James T. Kirk, Lieutenant Uhura, Lieutenant Commander Montgomery Scott, and Doctor Leonard McCoy – found the Terran vessel to belong to an extremely brutal regime, almost dictatorial in its command structure. Advancement through assassination was commonplace.

During the encounter, Captain James T. Kirk convinced the counterpart of his first officer, Spock, that the Empire could not sustain itself. Indeed, Spock predicted that in its current form, the Empire had just over two centuries before total collapse. (TOS episode: "Mirror, Mirror"; TOS novel: The Sorrows of Empire)

Shortly thereafter, Spock rose to become leader of the Terran Empire, proposing a series of reforms designed to make the Empire more secure and less-dictatorial in nature. These included a significant disarmament program. Unfortunately, once these reforms were complete, the Empire was unable to defend itself against the equally aggressive and powerful forces surrounding it. The Klingon-Cardassian Alliance overran the Empire, conquering Earth and leaving Terrans and Vulcans enslaved. (DS9 episode: "Crossover")

Spock's rise to power is detailed in The Sorrows of Empire.

During this time, the forces of the mirror universe began implementing safeguards to prevent another crossover event with the regular universe. Transporter design was altered to prevent interdimensional travel, requiring the creation of devices specifically for that purpose, including the multidimensional transporter. In the event of another crossover, those involved would be killed to prevent further interference. (DS9 episodes: "Crossover", "Through the Looking Glass")

In 2293, after being snared in the Janus Prime Vortex, Captain Hikaru Sulu and the crew of the USS Excelsior found themselves in the mirror universe, transposed into the bodies of their duplicates, aboard the ISS Excelsior. In order to return to their own universe, Sulu's crew were forced to use the Imperial starship and its fighters to escape from the Terran Empire, and enlist the aid of the Klingon Alliance and the Romulan Republic in fighting the Tholian Empire to gain access to the Janus Ultima Vortex. (TOS video game: Shattered Universe)

24th century[]

By the early 24th century the Terrans had been reduced to a slave-race and a handful of rebels on the run from the Klingon-Cardassian Alliance, which was intent on destroying the entire Terran race. One such ships used by the Terran Rebellion was Stargazer, captained by Gilaad Ben Zoma. (STA novel: Three)

The circumstances faced by the Terran race as depicted in the 2017 Mirror Broken comic book series differs substantially from those seen in the Star Trek: Mirror Universe prose works — specifically, the Terran Empire still exists in rump-form, with humanity having been driven all the way back to the Sol system by the Klingon-Cardassian Alliance by the 2360s or 2370s and militarily contained there, and with Mirror Spock's reforms having largely failed as policy. These circumstances seemingly somewhat conflict with the information given in the DS9 episode "Crossover," but in this series, the events seen onscreen in DS9 still evidently canonically take place.

Bajor, formally occupied by the Terrans was freed by the Alliance and soon joined it, in orbit the command post/ore processing facility Terok Nor was constructed.

By 2370, the second major contact with the primary universe took place. A runabout from station Deep Space 9 entered the mirror universe following an incident in the Bajoran wormhole. Kira Nerys and Julian Bashir were captured by forces from Terok Nor, and interrogated by the commander, Intendant Kira Nerys. Bashir was sent to work in the ore processing plant, where he befriended Miles O'Brien. After instigating a series of incidents aboard the station, including the death of Odo during a slave uprising, Kira and Bashir convinced privateer Benjamin Sisko to rebel against the Alliance and help them to escape back to the primary universe. (DS9 episode: "Crossover")

A year later, Smiley crossed over to the primary universe and impersonated his counterpart long enough to capture Benjamin Sisko. He took Sisko back to the mirror universe, where he convinced him to impersonate his mirror self who had been killed in a skirmish with Alliance ships. The rebels needed the other Sisko to win over Jennifer Sisko, Sisko's wife, who was working as a scientist for the Alliance. Jennifer had been developing a transpectral sensor array which would have allowed the Alliance to locate rebel hideouts in the Badlands. Fortunately for the rebels Ben was able to convince Jennifer to defect to the movement. (DS9 episode: "Through the Looking Glass")

In the Badlands, Chakotay, a former slave, commanded a ship in the rebellion attempting to evade pursuit. There he encountered a strange ship which had been catapulted seventy thousand light-years across the galaxy. (VOY novel: The Mirror-Scaled Serpent)

While in the Federation's universe, Smiley downloaded information from Deep Space 9's computers, including the plans for the USS Defiant. In 2372, the rebels constructed their own version of the Defiant, but had trouble getting it to function properly. Jennifer lured Ben Sisko back into the mirror universe to help. By this time the rebellion had grown in strength, culminating in the capture of Terok Nor, which became a rebel base of operations. (DS9 episode: "Shattered Mirror")

In 2374, Intendant Kira sent a thief, Bareil Antos to the primary universe to steal one of the Bajoran Orbs, believing it would permit Kira to unite Bajor under her rule. The attempt failed, and Bareil returned to the mirror universe without the orb. (DS9 episode: "Resurrection")

In 2375, Grand Nagus Zek, the leader of the Ferengi Alliance in the primary universe, used the multidimensional transporter to travel to the mirror universe, hoping to open up business opportunities; however, he was captured and held hostage by the Alliance. Intendant Kira made arrangements with Worf, the Regent of the Alliance, to obtain a Klingon cloaking device from the primary universe in exchange for Zek's return.

She sent Ezri Tigan, a Trill mercenary and Kira's lover, to give Quark the ransom-demand. Quark and his brother Rom stole the cloaking device from Klingon General Martok's ship and delivered it to Ezri, but decided at the last minute that they couldn't trust her to keep her side of the deal, and accompanied her to the mirror universe. There, all three were captured by the Terran rebels, who planned to keep the cloaking device. Ezri's companion Brunt freed them, delivering them to Regent Worf.

Aboard Worf's flagship, Quark and Rom were imprisoned along with Zek upon discovering Kira's plan, only to be later rescued by Ezri as revenge against Kira for killing Brunt. Ezri ended up joining the rebel cause. The primary universe Ferengi were allowed to return to the primary universe for having aided the rebels' defeat of Worf, a major victory for the rebellion. (DS9 episode: "The Emperor's New Cloak"; DS9 novel: Saturn's Children)

Continuing events in the mirror universe are told in Saturn's Children.

In late 2376, Intendant Kira managed to use a form of mind-control to manipulate the primary-universe Jem'Hadar Taran'atar into doing her bidding. She had him attack Kira Nerys before fleeing Deep Space Nine, and eventually beamed him into the mirror universe. (DS9 novel: Warpath)

The continuing tale of events in the mirror universe are told in the novels Fearful Symmetry and The Soul Key.

From 2376 into 2381, after the fall of Terok Nor to the Cardassians, the Terran Rebellion united with the Mackenzie Calhoun and the remnants of the Romulan Empire along with the forces of Memory Omega with Jean Luc Picard as their leader to liberate Earth, where they then proceeded to liberate other core worlds of the Terran Empire. Instigating a war between the Klingons and the Cardassians, the Rebellion was able to sue for peace and create the Galactic Commonwealth, a representative republic that was in the process of rebuilding its member worlds. (ST - Mirror Universe novel: Rise Like Lions)

25th century[]

By the 25th century, the Terran Rebellion had succeeded in throwing off Alliance rule and a restored Terran Empire was once again a major power in the quadrant, possessing technology and weapons roughly on par with 25th-century Starfleet in the primary universe. Terran Empire ships and forces were known to operate in and around Cardassian territory, and even conduct missions to use the Bajoran wormhole to infiltrate the counterpart universe. (STO mission: "Crack in the Mirror")

Later history[]

In the 27th century the last known crossover between the primary and mirror universes took place. By the 32nd century the distance between the primary and mirror universes had become so great that the Federation believed it was no longer possible for crossovers between the two universes to take place. (DSC episode: "Die Trying")

Alternate mirror universes[]

It has not been officially recorded (since the discovery of the mirror universe itself is still relatively new to the Federation), but scientific research believes that there are multiple alternate mirror universes, as there have been recorded to be various alternate prime universe realities. In at least one alternate universe, the Terran Empire was not destroyed by the Klingon-Cardassian Alliance. A highly-organized resistance movement called the Maquis strongly-opposed the Terran Empire in the late 23rd century and for much of the 24th century.

In 2383, Starfleet Captain Typhuss James Kira visited this universe, when his shuttlecraft SC-4 was pulled into a temporal anomaly and arrived in this alternate mirror universe. He later returned to the primary universe with an alternate mirror Kira Nerys.

In another alternate universe, where there is a militaristic Bajoran-dominated governmental authority, the Bajoran Empire, controlling Bajor, Earth, Betazed and surrounding space through the use of the powerful Bajoran Militia.




  • ENT: "In a Mirror, Darkly"
  • DSC
    • "Into the Forest I Go"
    • "Despite Yourself"
    • "The Wolf Inside"
    • "Vaulting Ambition"
    • "What's Past is Prologue"
  • TOS: "Mirror, Mirror"
  • DS9:
    • "Crossover"
    • "Through the Looking Glass"
    • "Shattered Mirror"
    • "Resurrection"
    • "The Emperor's New Cloak"