2375

Multiple realities
(covers information from several alternate timelines)

Events

Prime universe

The Phage has supposedly been cured during this year by the Think Tank. (VOY: "Think Tank")
Captain Kathryn Janeway learns that a family tale about one of her ancestors, Shannon O'Donnell, has been exaggerated. (VOY: "11:59")
Voyager encounters the USS Equinox, another Starfleet vessel stranded in the Delta Quadrant. The Equinox crew had since broken the Prime Directive and killed several nucleogenic lifeforms for use as a fuel source to power an enhanced warp drive. The Equinox eventually deserted Voyager after stealing a new shield emitter designed to prevent the lifeforms from attacking. Voyager is attacked by the aliens. (VOY: "Equinox")
Ezri Tigan is joined to the Dax symbiont. (DS9: "Image in the Sand")
The Romulan Star Empire constructs a hospital on one of Bajor's moons, Derna, but also equips it with several thousand plasma torpedoes. Colonel Kira Nerys leads a blockade of the moon in protest, and the situation is eventually resolved when Starfleet Admiral William Ross threatens the Romulans with Federation intervention. (DS9: "Image in the Sand", "Shadows and Symbols")
The IKS Rotarran destroys the Monac shipyards by triggering a solar flare after Worf, Martok, Miles O'Brien, Julian Bashir, and Quark undertake the mission in the late Jadzia Dax's name in order to enable her spirit to enter Sto-vo-kor. (DS9: "Shadows and Symbols")
Benjamin Sisko (accompanied by his son, father and Ezri Dax) finds the Orb of the Emissary. The Bajoran wormhole is reopened and Sisko returns to Deep Space 9. (DS9: "Shadows and Symbols")
Elim Garak suffers an emotional breakdown under the pressure of helping Starfleet to wage war against his Dominion-occupied homeworld. Ezri Dax helps him to recover, and subsequently decides to remain on Deep Space 9 to become the station's counselor. (DS9: "Afterimage")
The USS Voyager enters a sparsely-populated region of space called the Void. While there, they discover a subspace vortex which brings them two thousand light years closer to home. (VOY: "Night")
Vulcan Captain Solok challenges old rival Benjamin Sisko to a game of baseball. Sisko's 'Niners' team is defeated by Solok's 'Logicians' in a match in one of Quark's holosuites. (DS9: "Take Me Out to the Holosuite")
Doctor Julian Bashir performs an operation on Sarina Douglas that frees her from her catatonic state. (DS9: "Chrysalis")
The Voyager crew builds the Delta Flyer shuttlecraft. (VOY: "Extreme Risk")
B'Elanna Torres suffers severe internal injuries from running high risk holo programs with the safety protocols off. (VOY: "Extreme Risk")
A defective clone of the Vorta Weyoun attempts to defect to the Federation, but ultimately sacrifices himself to save Odo's life. Before he dies, he tells Odo that a sickness (later identified as the morphogenic virus) is spreading through the Great Link and is killing the Founders. (DS9: "Treachery, Faith and the Great River")
Species 8472 creates a simulation of Earth on a space station in the Delta Quadrant to train individuals of their species to infiltrate Starfleet Command. The USS Voyager later convinces them that the Federation is not a threat. (VOY: "In the Flesh")
Aging Klingon legend Kor seeks Worf's help to obtain a command so that he can feel useful in the Dominion War. He later stops Worf from commanding a suicide mission against ten Jem'Hadar ships, instead leading the mission himself, thus stepping out of life and into history in a blaze of glory. (DS9: "Once More Unto the Breach")
B'Elanna Torres refuses to take medical treatment that will save her life from from a holographic representation of infamous Cardassian Doctor Crell Moset. (VOY: "Nothing Human")
The USS Defiant visits AR-558 on the front line of the battle with the Dominion. Upon seeing the losses the Starfleet unit stationed there has taken, Benjamin Sisko decides to stay until further reinforcements arrive. They are successful in holding a captured Dominion communications array at AR-558, but take heavy losses. Nog loses a leg after being shot by a Jem'Hadar soldier. (DS9: "The Siege of AR-558")
Voyager attempts to use quantum slipstream drive once again. The ship travels 10,000 light years before the slipstream collapses. The technology is deemed too dangerous for repeated use. (VOY: "Timeless")

In an alternate timeline, Voyager is destroyed as a result of problems with the slipstream. The Delta Flyer, which had attempted to map the slipstream before Voyager, returns to Earth, with Harry Kim and Chakotay. (VOY: "Timeless")

Kira Nerys is transported to Empok Nor, where she discovers that Dukat is now the leader of the Cult of the Pah-wraiths. (DS9: "Covenant")
Nog returns to Deep Space 9 from Starbase 235, where he has received counseling and a replacement leg. Utterly unable to cope with life after AR-558, he retreats into the holographic refuge of Vic Fontaine's lounge. (DS9: "It's Only a Paper Moon")
The Evora become protectorate members of the United Federation of Planets. (Star Trek: Insurrection)
Admiral Matthew Dougherty of Starfleet and the Son'a attempt a forced relocation of the Ba'ku in order to harvest the metaphasic radiation from their planet's rings. Captain Jean-Luc Picard and the USS Enterprise-E crew stage a rebellion, and convince the Federation Council to allow the Ba'ku to remain on their planet. (Star Trek: Insurrection)
Commanders William T. Riker and Deanna Troi resume their relationship. (Star Trek: Insurrection)
Miles O'Brien disappears on New Sydney while trying to find Morica Bilby. Ezri Dax returns home to use her mother Yanas' influence to help find him. She discovers that her brothers are involved with the Orion Syndicate, and that her younger brother Norvo murdered Bilby. (DS9: "Prodigal Daughter")
Tom Paris is demoted to the rank of ensign for insubordination and serves 30 days in the brig in connection with an unauthorized circumvention of the Prime Directive at a planetoid occupied by the Moneans and the resultant damage to the Delta Flyer. (VOY: "Thirty Days")
Lieutenant Chu'lak carries out a spree of murders aboard Deep Space 9 before he is stopped by Lieutenant Ezri Dax, who has psychological help from murderous former host Joran Dax. (DS9: "Field of Fire")
Odo discovers another of the Hundred, Laas. The Changeling lives on Deep Space 9 for a time, before killing a Klingon. Kira Nerys helps him escape. (DS9: "Chimera")
A jack-in-the-box in the Bashir 62 holoprogram causes Vic Fontaine to lose control of his casino to Frank Chalmers. The Deep Space 9 crew stage a daring heist to steal it back from the mob. The plan is successful and Vic's Lounge returns to normal. (DS9: "Badda-Bing, Badda-Bang")
A joint Federation/Romulan Conference is held on Romulus. With the co-operation of Admiral William Ross, and the reluctant assistance of Julian Bashir, Section 31 uses the conference to meddle in Romulan politics and ensure that Kimara Cretak does not get a seat on the Continuing Committee. (DS9: "Inter Arma Enim Silent Leges")
Benjamin Sisko buys twelve hecapates of land on Bajor, and makes plans to build a house there for his retirement. He asks Kasidy Yates to marry him and, after she accepts, asks his son, Jake, to be best man. Sisko is later warned by the Prophets not to go ahead with the marriage. (DS9: "Penumbra")
Worf takes command of the IKS Koraga, which is later destroyed. He manages to leave the ship in an escape pod, and is rescued by Ezri Dax. However, they are subsequently captured by the Breen. (DS9: "Penumbra")
Dukat is surgically altered to resemble a Bajoran. (DS9: "Penumbra")
Voyager raids a Borg sphere and steals a transwarp coil, which allows it to travel 20,000 light years. Seven of Nine is lured back to the Borg Collective by the Borg Queen, but she is later rescued by the Voyager crew. (VOY: "Dark Frontier")
The alternate Voyager created by the "Silver Blood" of the Class Y planet begins to lose molecular cohesion as a result of exposure to a new enhanced warp drive. The crew is able to realize their predicament, but Captain Kathryn Janeway refuses to seek shelter at a Y-class world until it is too late. The crew attempts to launch a message drone with information about their history, but the drone is destroyed and the ship disintegrates before it can contact the real Voyager. (VOY: "Course: Oblivion")
Benjamin Sisko and Kasidy Yates are married aboard Deep Space 9. (DS9: "'Til Death Do Us Part")
The Breen Confederacy becomes formally allied with the Dominion. (DS9: "'Til Death Do Us Part", "Strange Bedfellows")
The Breen attack on Earth takes place, in which Earth, specifically San Francisco, is attacked and severely damaged by Breen forces. (DS9: "The Changing Face of Evil")
In league with the surgically altered Dukat, and under the influence of the Pah-wraiths, Kai Winn Adami consults the ancient and forbidden Book of the Kosst Amojan in order to learn how to release the Pah-wraiths from the Bajoran Fire Caves. (DS9: "The Changing Face of Evil")
The USS Defiant is destroyed by a Breen energy dampening weapon in the Second Battle of Chin'toka. (DS9: "The Changing Face of Evil")
Determined to free his world from Dominion occupation, Damar forms and leads the Cardassian Rebellion. (DS9: "The Changing Face of Evil")
Kira Nerys is given a temporary commission of Starfleet Commander and, together with Odo and Elim Garak, travels to Cardassia to assist Damar with the Cardassian Rebellion against the Dominion. (DS9: "When It Rains...")
Odo learns that he is infected with the same morphogenic virus that is killing the Founders. Doctor Julian Bashir discovers that the virus was created by Section 31, and that they used Odo to transmit it to the Great Link. (DS9: "When It Rains...")
General Martok assumes the leadership of the Klingon Empire as Chancellor of the Klingon High Council after Lieutenant Commander Worf kills former chancellor Gowron in a duel. (DS9: "Tacking Into the Wind")
Julian Bashir uses illegal Romulan mind probes to extract information about the morphogenic virus from the mind of Section 31 operative Luther Sloan; Sloan commits suicide during the procedure. Bashir subsequently produces a cure, and successfully administers it to Odo. (DS9: "Extreme Measures")
In an alternate timeline, Voyager is destroyed by a temporal disruptor planted by Captain Braxton from the 29th century. Fortunately, the crew of the USS Relativity, aided by Seven of Nine from this year, prevent the disaster. (VOY: "Relativity")
The USS Sao Paulo is renamed the USS Defiant under the command of Captain Benjamin Sisko. (DS9: "The Dogs of War")
Rom succeeds Zek as Ferengi Grand Nagus. (DS9: "The Dogs of War")
Kasidy Yates-Sisko announces that she is pregnant with Benjamin Sisko's child. (DS9: "The Dogs of War")
Damar's Cardassian Rebellion is crushed, but Cardassian citizens rise up against the Dominion. In response, the Jem'Hadar begin to destroy Cardassian cities, killing millions of people. Damar is killed in an attempt to storm Dominion Headquarters. (DS9: "What You Leave Behind")
The Dominion War comes to an end after the alliance of the Federation, the Klingon Empire, and the Romulan Star Empire, together with the turncoat Cardassian fleet, takes control of the Cardassian system at the Battle of Cardassia. In the captured Dominion Headquarters, Odo cures the Female Changeling of the morphogenic virus and she subsequently orders Dominion forces to surrender. (DS9: "What You Leave Behind")
Following the end of the Dominion War and the liberation of Cardassia, Elim Garak remains on Cardassia, his exile from his homeworld now officially over. (DS9: "What You Leave Behind")
The Chief of Operations of Deep Space 9, Miles O'Brien, and his family leave the station to return to Earth; O'Brien takes up a position at Starfleet Academy as Professor of Engineering. (DS9: "What You Leave Behind")
At the request of Chancellor Martok, Worf becomes the Federation Ambassador to Qo'noS. (DS9: "What You Leave Behind")
Odo leaves the Alpha Quadrant to rejoin the Founders in the Great Link, curing them of the morphogenic virus. (DS9: "What You Leave Behind")
Captain Benjamin Sisko is lost, presumed dead, in the Fire Caves on Bajor, together with the former Cardassian leader, Dukat, and the Bajoran spiritual leader, Kai Winn Adami. The Bajorans begin the process of electing a new Kai. Benjamin Sisko later appears to his wife, Kasidy Yates-Sisko, and tells her that he is with the Prophets in the Celestial Temple. (DS9: "What You Leave Behind")
Richard Bashir is released from prison this year. (DS9: "Doctor Bashir, I Presume")
The Brunali homeworld is attacked by the Borg Collective. (VOY: "Child's Play")

Mirror universe

Grand Nagus Zek crosses over to the mirror universe and is captured by the Klingon-Cardassian Alliance. Quark and Rom are able to free him by giving Regent Worf a cloaking device from the IKS Rotarran. Worf's plan to attack Terok Nor fails and he is captured by the Terran Rebellion. (DS9: "The Emperor's New Cloak")
Jadzia Dax, Brunt, and Elim Garak are killed. (DS9: "The Emperor's New Cloak")

Appendices

Notes

The time placement of Star Trek: Insurrection is highly speculative; it is placed roughly concurrent with DS9: "It's Only a Paper Moon", since Worf is only in the opening scenes of that episode, which spans quite a bit of time, and doesn't appear again until the middle scenes of "Field of Fire" (which takes place over three weeks after "Paper Moon"), thus allowing him the time required to make the security upgrades to the Manzar colony and to join the Enterprise-E crew for Insurrection.
The Star Trek Chronology gives this date for the death of Deanna Troi in the anti-time future of TNG: "All Good Things...". This was based on the supposition that the crew of the Enterprise-D disbands concurrent with the end of TNG Season 7. No specific date is given in the episode itself.
According to the proposed treaty from "The Price", this treaty between the United Federation of Planets and the Barzanian Planetary Republic was set to expire in this year on stardate 52000. (TNG: "The Price")