Multiverse (Marvel Comics)

In 1977, Marvel Comics started depicted parallel universes to the main setting of their stories in the What If series, narrated by the Watcher and depicting alternate histories that diverged from the familiar Marvel Universe in key moments. In 1983, Alan Moore's Daredevils series featuring Captain Britain for Marvel UK explicitly introduced the travel between the alternate worlds, establishing that each was protected by its own version of Captain Britain, collectively known as Captain Britain Corps. The series was also the first to refer to the alternate words by the Earth-### numerical designations, establishing the home reality of the Brian Braddock version of Captain Britain as Earth-616. That number carried over into the American Marvel Comics through the Excalibur series also featuring Captain Britain and has been used to refer to the "main" Marvel Universe ever since.

In 1992, Senior Editor Mark Gruenwald, creator of the Official Handbook of the Marvel Universe, wrote "Marvel's official rules of time travel" in Marvel Age #117. These established that each act of time travel always produces an alternate universe, diverging it from the original timeline in which the time travel never took place. This led to alternate futures from storylines such as Days of Future Past and Age of Apocalypse being classified as alternate realities within the Multiverse, persisting even after they were supposedly "undone" by the actions of time-travelers. In Nightcrawler #1 (1985) the X-Men traveled into the reality of a fairy tale which Kitty Pryde had previously seemingly "invented" in Uncanny X-Men #153 (1981). This established the precedent of in-universe fiction representing the factual truth of alternate realities, later explicitly confirmed by the Official Handbook.

During the 2000s, Marvel began consistently numbering prominent alternate universes in the issues of the Official Handbook, beginning with one-shot handbooks published in 2004-2005 and later publishing a comprehensive numbered list in the Appendix to the Official Handbook of the Marvel Universe A to Z (2008). The list included designations for alternate universes seen in comics books such as Marvel Comics 2, Marvel 2099, and Exiles, but also various film and television series based on Marvel Comics, establishing adaptions in non-comic media as part of the wider Marvel Multiverse. At the end of the printed list, a link was provided for the online Appendix which remained consistently updated and as of 2026 is approaching 4,000 entries. The online list extended the designations to stories published by Marvel but lacking any familiar Marvel superheroes, including creator-owned stories published under the Epic Comics imprint, licensed comics including Heathcliff and ALF, and original series by CrossGen and Malibu Comics, publishers that were later fully acquired by Marvel. The classification system for alternate realities was devised, in part, by Mark Gruenwald.

Numeric designations originating from the Handbooks and the online Appendix have sporadically been used within Marvel Comics, video games, and the 2023 film Spider-Man: Across the Spider-Verse, confirming their canonicity. However, during the publication of the "Spider-Verse" storyline in 2014, writer Dan Slott had stated on Twitter that the numbers that appear in handbooks do not count, and only those that are published within "actual" stories do. This was in response to some reality numbers in the pages of Spider-Verse not matching the previous designations, such as the home reality of Spider-Ham, previously Earth-8311, being re-designated as Earth-25 instead. Subsequent Handbooks have dealt with contradictions both ways: while the attempted change of Spider-Ham's reality had been ignored, the home reality of Spider-Woman (Gwen Stacy) previously numbered by the online appendix had been adjusted to that used in the pages of the comics.

A glossary of terms was provided in the Official Handbook of the Marvel Universe A-Z Volume 2 (2008):

• Dimension - an area of interest containing space, time, matter, and energy. A dimension can be virtually infinite or clearly finite, "Earth-like" or guided by magic or alien physics.
• Universe - a single dimension, such as Earth-616, the Prime Marvel Universe.
• Reality - a collection of an Earth-like universe and the various other dimensions associated with it, such as the Microverse, the Dark Dimension, and the Negative Zone. Versions of these dimensions exist in most alternate realities.
• Multiverse - a collection of alternate realities with a similar nature and a universal hierarchy.
• Megaverse - a larger selection of alternate realities that lack a common hierarchy.
• Omniverse - a collection of every single universe and dimension. The Omniverse contains the real world plus every possible fictional reality, including all the works that are outside of Marvel's copyright restrictions, and therefore also outside the Marvel Multiverse. This was based on Mark Gruenwald's original definition of the term.

While the Official Handbook tends to stick to the nomenclature of "alternate realities", various comic writers had used "alternate universes", "alternate timelines", and "alternate dimensions" interchangeably.

Originally, there was only one universe, the First Firmament. Due to the actions of Celestials existing there, it diverged. Then, the Multiverse went through several incarnations and eventually the Big Bang caused the existence of the Seventh Cosmos, where most well-known heroes originated. The Marvel multiverse is protected from imbalance by the Living Tribunal, a cosmic entity, who is one for the entire multiverse. It may act to prevent one universe from amassing more power than any of the others or from upsetting the cosmic balance in some way. It is only overseen by the One-Above-All, an omnipotent entity said to have created the entire Marvel Multiverse.

According to Forge, mutants living on these alternate Earths have lost their powers due to the M-Day happening on Earth-616, as stated in "Endangered Species". However, this mass depowering has not been seen in many of Marvel's current alternate reality publications such as the Exiles, the Ultimate Marvel titles, Amazing Spider-Girl, the Marvel Adventures titles or GeNext. This was apparently retconned during the "X-Men: Messiah Complex" storyline, where Forge stated that all mutants in possible future timelines were depowered, not in parallel universes. This, in addition to A.R.M.O.R.'s observation that Lyra arrived from an alternate reality indicates that the topology of the Marvel Multiverse is based on new realities branching off from key nodes of a timeline instead of strictly parallel dimensions.

In the 2015 Secret Wars series, a confrontation with the Beyonders over the fate of the various alternate versions of Molecule Man results in the destruction of the Multiverse, triggering various 'incursions' as Earths crash together and destroy each other, the Beyonders' assault culminating in Doctor Doom stealing the power of the remaining Beyonders and bringing the remaining universes together into a single 'Battleworld'. Molecule Man, who had been the source of Doom's power, transfers Doom's power to Mister Fantastic when Doom acknowledges that Reed would have done a better job as 'God' than he did. Having restored Earth-616 as it was before the Beyonders' incursions began, Mister Fantastic departs to recreate the multiverse with the company of his restored family. The seventh iteration of the Multiverse was destroyed and was reborn as the eighth.

Below is a short, non-comprehensive list of some of the most noteworthy and significant universes in the Marvel Multiverse. Most of these were designated in the Official Handbook of the Marvel Universe in either the physical print or the digital Appendix.