Alternate reality

An alternate timeline is a parallel universe that has been created by altering one or more events in one's subjective 'past', usually unintentionally.

22nd Century Alternate Timelines
In 2152, Captain Jonathan Archer's removal from history by Daniels created a timeline in which Earth of the 29th century was devastated. (ENT episode: "Shockwave")

In 2153, the Enterprise crossed over into a timeline in which the Daedalus had not been destroyed. (ENT novels: Daedalus and Daedalus's Children)

Later that year, a timeline was created in which Archer brain injuries left him no longer fit for command, leading to the destruction of Earth by the Xindi and the near extinction of humanity. (ENT episode: "Twilight")

In 2154, a timeline was created in which an attempt by the Enterprise to enter a subspace corridor sent it over a century into the past. (ENT episode: "E²")

Later that year, the Enterprise encountered a timeline in which the Na'kuhl had aided Nazi Germany in World War II. (ENT episodes: "Zero Hour" and "Storm Front")

23rd Century Alternate Timelines
In 2266, a timeline was created in which James T. Kirk died on Grex in 2247. (TOS trilogy: The Janus Gate)

In 2267, Doctor Leonard H. McCoy traveled through the Guardian of Forever to 1930, creating a timeline in which Edith Keeler died not die in a traffic accident. (TOS episode: "The City on the Edge of Forever" and TOS novel: Provenance of Shadows)

In one timeline, James T. Kirk and Spock failed to prevent McCoy from saving Keeler. (TOS short story: "Triptych")

In another, Keeler was brought to the 23rd century, thus preserving history while allowing her to live. (short story: "Remembering the Future")

Later that year, the Enterprise made first contact with the Mirror Universe. (TOS episode: "Mirror, Mirror")


 * ''See Mirror Universe article for other crossovers with the main Mirror Universe and alternate Mirror Universes.

In 2268, the Romulans created a timeline in which the Federation never existed. (TOS novel: Killing Time

In 2269, a timeline was created in which Spock died on Vulcan as a child. (TAS episode: "Yesteryear")

Towards the end of the year, the Clan Ru created a timeline in which dinosaurs never became extinct and humans never evolved. (TOS novel: First Frontier)

In one timeline, Kirk was abducted by Kor, subjected to a Klingon mind sifter, and transported through the Guardian of Forever to 1950s Earth. (TOS short story: "Mind-Sifter")

In 2293, a timeline was created in which Spock was assassinated at Khitomer. (TOS novel: Assignment: Eternity)

24th Century Alternate Timelines
In 2366, a timeline was created in which the removal of the Enterprise-C from 2344 resulted in war between the Federation and the Klingons. The Tasha Yar of this timeline joined the crew of the Enterprise-C, and later became the mother of Sela. (TNG episode: "Yesterday's Enterprise")

In 2368, a timeline is created when a Sindareen from 2408 murders Deanna Troi. (TNG novel: Imzadi)

In 2369, Jean-Luc Picard, with the aid of Q, created a timeline in which he did not get into a fight with a group of Nausicaans in his youth. (TNG episode: "Tapestry")

In 2370, Montgomery Scott traveled back to 2293 and rescued Kirk from his apparent death on the Enterprise-B, creating a timeline in which the Borg invasion of 2063 was successful. (TNG novel: Engines of Destiny)

Later that year, Worf encountered many alternate timelines before returning to his own universe. (TNG episode: "Parallels")

Towards the end of the year, Q manipulated Picard into creating an anti-time anomaly that created multiple alternate timelines. (TNG episode: "All Good Things..."

In 2371, members of the crew of Deep Space 9 accidentally created a timeline in which the social reforms that followed the Bell Riots never occurred. (DS9 episode: "Past Tense")

Later that year, the USS Voyager accidentally created a timeline in which a civilization in the Delta Quadrant was destroyed. (VOY episode: "Time and Again")

Later that year, Miles O'Brien encountered several alternate timelines before dying of radiation sickness and being replaced by his counterpart. (DS9 episode: "Visionary")

Later that year, while Kirk lay dying on Veridian III, the Organians showed him a timeline in which he had resigned from Starfleet following his initial encounter with the Guardian of Forever. (TOS short story: "Reflections")


 * Some have speculated that Kirk's revival through Borg technology and his subsequent adventures in the 24th century occur in an alternate timeline and not the main Star Trek'' timeline.

In 2372, Harry Kim found himself in a timeline in which he had never joined the Voyager crew. (VOY episode: "Non Sequitur")

Later that year, the removal of Benjamin Sisko from normal space-time created an alternate timeline in which Jake Sisko spent the rest of his life trying to get his father back. (DS9 episode: "The Visitor")

In 2373, the Borg created a timeline in which Earth had been assimilated since 2063. (TNG movie: Star Trek: First Contact)

Later that year, a timeline was created in which the USS Defiant traveled back in time 200 years and crashed on a planet in the Gamma Quadrant, forcing the crew to colonize it. (DS9 episode: "Children of Time")

In one timeline, Kathryn Janeway and B'Elanna Torres were killed in a Krenim attack this year. (VOY episode: "Before and After")

In one timeline, Captain Braxton believed that Voyager would be responsible for accidentally destroying Earth in the 29th century, and attempted to prevent this by destroying Voyager first (VOY episode: "Future's End").

In 2374, several alternate timelines were created by Krenim officer Annorax's attempts to restore his people's former glory. (VOY episode: "Year of Hell")

Later that year, a timeline is created in which the opening of a second wormhole in the Bajoran system destroys Deep Space 9. (DS9 trilogy: Millennium)

In 2375, an attempt to use a quantum slipstream drive to return Voyager to the Alpha Quadrant created a timeline in which the ship crashed on an ice planet, killing everyone aboard and leaving Chakotay and Harry Kim as the only surviving crewmembers. (VOY episode: "Timeless")

Later that year, a Braxton from an alternate timeline attempted to destroy Voyager again, but was prevented by Seven of Nine. (VOY episode: "Relativity")

In one timeline, Kes traveled back in time from 2376 to 2371, where she attempted to turn Voyager over to the Vidiians. (VOY episode: "Fury")

In 2377, Chakotay was aided in restoring a temporally-shattered Voyager by the adult Naomi Wildman and Icheb from an alternate timeline. (VOY episode: "Shattered")

In 2378, Voyager returned to Federation space thanks to the aid of an Admiral Janeway from a timeline in which Voyager did not return until 2394. (VOY episode: "Endgame")