I just finished watching Star Trek:TOS. There were at least two episodes dealing with other dimensions, the mirror universe and the anti-matter universe.

How many "universes" are there in Star Trek canon, and is any reason given that explains their existence or how they exist alongside each other?

1 Answer 1


A few answers come to mind:

  • There's the Mirror Universe from TOS, which reappears in later series. It seems to be connected to the primary universe in some way.
  • There's the antimatter universe, from TOS.
  • There's a near-unlimited number of quantum realities seen in TNG 7x11, "Parallels".
  • Then there's the alternate timeline created for the 2009 movie.

As far as I know, it is unknown if there's any overlap from these. The Mirror Universe, Antimatter Universe, and 2009 Movie may or may not be a quantum reality from Parallels.

And in addition to the above, which specifically fall under "parallel universe", there are other dimensions/universes that seem unlikely to fall under that umbrella term: Fluidic Space, the Q Continuum, and the one Dax accidentally created, for example.

  • 1
    I would suppose there are even uncountably infinite many "quantum realities" in Parallels. But I have no transcript to back that up.
    – bitmask
    Feb 5, 2012 at 2:58
  • I think Parallels makes it clear that they believe an essentially infinite number of parallel universes exists.
    – BBlake
    Feb 5, 2012 at 17:43
  • there is also a "parralel universe" episode in star trek enterprise,but it may be the same as the mirror universe in TOS.the episode is in season 4 i think. Feb 5, 2012 at 19:42
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    @sam Yep, ENT 4x18 "In a Mirror, Darkly" is a direct sequel to the TOS 3x09 "The Tholian Web". It reveals what happened to the USS Defiant that the TOS Enterprise was looking for - it ended up in the Mirror Universe and a century or so back in time. (As a side note, this is the episode that canonizes the TOS ship designs as an in-universe stylistic choice, not a limitation of reallife technology)
    – Izkata
    Feb 5, 2012 at 20:49
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    Also, I would include fluidic space as an "alternate dimension". Jun 7, 2013 at 23:20

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