Federation universe

The "Federation" universe was a parallel universe where Earth was part of the United Federation of Planets meta-government from the 23rd and 24th centuries onward.

This universe was joined together with the Doctor's universe by a faction of Cybermen so that they could form an alliance with the Borg, a similar cybernetic race native to this universe. The only known people who were aware of the two universes having been merged were the Eleventh Doctor and Guinan.

While the planet Earth and humans existed in both universes, some of the species native to the Federation universe were not known to exist in the Doctor's universe, including the Borg, the Klingons, the Vulcans and the Deltans. Aside from the Federation itself, major powers included the Klingon Empire and the Borg Collective.

Following the Doctor and the crew of the USS Enterprise defeating the intruding Cybermen, the Doctor speculated that all the influences of N-Space had been removed from this reality before he, Amy and Rory returned to N-Space. (COMIC: Assimilation²)

Alternate timeline
In a potential history shown by the Eleventh Doctor to Jean-Luc Picard, the Cybermen, having integrated both the Doctor's N-Space and Picard's parallel universe, successfully conquered the Borg Collective and began a campaign to convert the galaxy.

Throughout the 25th century, the Cybermen converted the Klingons by 2418, the Raxacoricofallapatorians by 2448, the Vulcans by 2468, and the Judoon by 2493. By 2533, the Cybermen had conquered Earth and vanquished San Francisco's Starfleet Academy, the last holdout of free humanity. (COMIC: Assimilation²)

Behind the scenes
This universe is the setting of the Star Trek franchise and appears in relation to Doctor Who only in the Assimilation² crossover comic. In addition to his work on Assimilation², artist J. K. Woodward published a number of pieces combining elements of the Doctor Who and Star Trek universes.
 * A Borg drone and a Cybus Cyberman drone stand in the open doorway of the Doctor's TARDIS.
 * Borg-assimilated Face of Boe.
 * and the Eleventh Doctor swap costumes.
 * Borg and "Early CyberFaction" Cyberman.
 * Spock gleans the image of jelly baby in a with the Fourth Doctor.
 * Borg-assimilated Vashta Nerada.
 * A phaser-wielder with tally marks and the Eleventh Doctor with sonic screwdriver in hand faces a pair of Borg-assimilated Silents.
 * River Song dressed as a Klingon holding a Bat'leth.
 * The Doctor's TARDIS appears in front of a Klingon Bird-of-Prey.
 * The Ninth Doctor's counterpart in the Star Trek mirror universe.
 * The Tenth Doctor's counterpart in the Star Trek Terran Empire mirror universe.
 * The Eleventh Doctor's counterpart in the Star Trek Terran Empire mirror universe.
 * The Fourth Doctor faces the.
 * Amy Pond in a 23rd century Starfleet uniform, holding a tricorder.
 * A trio of CyberMondasians.
 * Starfleet officer in Borg alcove.
 * Worf converted into a Cyberman in the fashion of Craig Owens in Closing Time.
 * Borg-modified CyberTelosian Controller and two CyberTelosians.
 * Data and the Fourth Doctor laughing in the TARDIS.
 * Borg drone faces the Eleventh Doctor.
 * A pair of Borg-modified CyberMondasians.
 * The Fourth Doctor within a Borg vessel.
 * Borg-modified CyberMondasian.
 * Borg-assimilated Ood.
 * Amy Pond in Starfleet uniform with Captain James T. Kirk and the Eleventh Doctor.
 * faces ().
 * Borg-assimilated Spock.
 * Spock converted into a Cyberman in the fashion of Craig Owens in Closing Time.
 * Borg drone.
 * and CyberTelosian.
 * Borg-assimilated Silent.
 * Borg-assimilated Ood.
 * Borg-assimilated Prisoner Zero.
 * Cyber-conversion.
 * Borg-assimilated Bannakaffalatta the Zocci.
 * Borg-assimilated Raxacoricofallapatorian.
 * Borg-assimilated Sontaran.
 * Adipose and.
 * The Eleventh Doctor and Spock face a.
 * Spock within the "coral" TARDIS control room.
 * Borg-modified Cybus Cyberman.
 * The TARDIS on the of the USS Enterprise (NCC-1701-D), above the.
 * Borg and Cybus Cybermen enter the "coral" TARDIS control room.
 * The TARDIS on the saucer section of the USS Enterprise (NCC-1701-D), at the.
 * The TARDIS with the s of the USS Enterprise (NCC-1701).
 * Borg-assimilated Silent.
 * Borg drone faces CyberTelosian.
 * Borg-assimilated Silurian warrior (The Hungry Earth).
 * Borg-assimilated Silurian scholar (Doctor Who and the Silurians).
 * Borg-assimilated Judoon.
 * Borg-modified CyberMondasian.
 * Borg-assimilated Prisoner Zero.
 * Borg-assimilated Ood.
 * Borg-assimilated Raxacoricofallapatorian.
 * Borg-modified Cybus Cyberman.
 * Borg-assimilated Vashta Nerada.
 * Mirror universe Tenth Doctor.
 * Borg-modified Cyber-Controller.
 * Doctor Martha Jones, and Nyota Uhura.
 * Amy Pond in Starfleet uniform with Captain Kirk and the Eleventh Doctor.
 * Borg-assimilated Prisoner Zero (colour).
 * Borg-assimilated Ood (colour).
 * Borg-assimilated Bannakaffalatta the Zocci (colour).
 * Borg-modified CyberMondasian (colour).
 * Borg-assimilated Silurian scholar (colour).
 * Borg-assimilated Raxacoricofallapatorian (colour).
 * Borg-assimilated Silurian warrior (colour).
 * Empress of the Racnoss faces the.
 * Borg-assimilated Sontaran (colour).
 * Borg-assimilated Silent (colour).
 * The Fourth Doctor within a Borg vessel (colour).