- For the behind the scenes concept, see shared multiverse.
- "So, Jay is saying he's from, like, a mirror-world. Or a parallel universe that's very, very similar to ours."
- "Multiverse would be a more apt description."
- —Cisco Ramon and Martin Stein[src]
The multiverse is a concept that refers to the existence of infinite universes that comprise everything that is. Each universe within the multiverse is referred to as a different "Earth", and each vibrates at a different frequency so that they cannot normally interact with or be seen by each other. If one is able to travel fast enough it is possible to breach the laws of physics and travel between these Earths.
- "This is our earth. Let's call it Earth One. And this second Earth, let's call it Earth Two. This is where Jay claims to be from. And these other earths, three, four, five, to infinity, all of them, are nearly identical to ours. And they all exist at the same time, giving us endless alternatives to what we have here. For example, the Joe West on Earth Two, your doppelganger, he might not be a detective. He could be a Nobel Prize-winning physicist. And you, the Barry Allen here is The Flash, but over there, he could be an electrician."
- —Martin Stein explaining the multiverse[src]
In early 2015, Barry Allen and the rest of Team Flash accidentally opened a singularity above Central City; though they succeeded in closing it, a series of 52 breaches between Earths One and Two were opened throughout the city as a result of their actions.
Between mid to late 2015 and early 2016, an Earth Two speedster known as Zoom began exploring the multiverse before using the breaches to launch an assault on Earth One's Central City in an attempt to steal The Flash's speed. Zoom sent numerous meta-humans through the breaches, each tasked with killing The Flash, but none succeeded. Team Flash, in an effort to stop Zoom's onslaught, systematically sealed each of the breaches, leaving only one open on a lower level inside S.T.A.R. Labs. Barry, Cisco Ramon, and Harrison Wells used the breach to travel to Earth Two in order to rescue Jesse Quick, sealing the breach upon their return.
Attempting to increase his speed, Barry Allen used a tachyon device, which in turn caused him to run too fast and accidentally create a breach between Earth One and Earth Thirty-Eight, the parallel world that is the home of Supergirl.
During his travels, Zolomon discovered that Earth One happened to be in the center juncture of the entire Multiverse, and that from there one could travel to any of the other infinite number of Earths. Enthralled by the idea of conquering all of existence, in May of 2016 he attempted to use the Mercury Labs Magnetar to instantaneously destroy every Earth in the Multiverse besides Earth One, using its central location as a means of targeting every other universe at the same time. Through the sacrifice of his own time remnant, Barry Allen was able to stop the device moments before it destroyed the Multiverse, and also managed to defeat Hunter in the process. Later, Harry decided to return to his life on Earth Two, and bid his farewells to the team.
Known parallel universes
- Earth One
- Earth Two
- Earth Three
- Earth Sixteen
- Earth Seventeen
- Earth Nineteen
- Earth Thirty-Seven
- Earth Thirty-Eight
- An unnamed Earth (home to CBS' The Flash)
- An unidentified Earth (home to Hells Wells)
- An unidentified Earth (home to the Francophone Harrison Wells)
- An unidentified Earth (a world which nearly destroyed Earth Nineteen)
- An unidentified Earth (a volcanic like Earth)
Possible parallel universes
- An unidentified Earth (a world where Kennedy was never assassinated)
- An unidentified Earth (a world where the Nazis won WWII)
Known extra-dimensional planes
Known parallel timelines
- Current timeline
- Original timeline
- 2046 Star City timeline
- Legion of Doom's alternate reality
- 2024 Central City timeline
Known constants in the multiverse
- Harrison Wells
- Henry Allen/Jay Garrick
- S.T.A.R Labs
- Big Belly Burger
- Super-intelligent gorillas
- Central City
- Star City/Starling City
- The Godfather
- Albert Einstein
- Beyoncé Knowles
- Mariah Carey
- Al Capone
- Super Mario
- Harry Potter
- Hamilton (musical)
- "Worlds Finest" (mentioned)
- "Missing" (mentioned)
- The fact that the number of breaches that opened in Central City is 52 can be seen as a possible reference to both the multiverse crisis storyline known as 52 and the New 52 imprint in the DC Comics.
- During an interview, the producers of the NBC television show "Powerless", jokingly referered to the Multiverse by saying that their show takes place on "Earth-P" as it was a DC Comics comedy. This is of course, unofficial and they actually revealed, at the time of the interview, that there was no plans to crossover with any other DC property, the show has since been cancelled.