Earth-616 is where most of the comics Marvel publishes takes place.

Why 616?

The term Earth-616 was first used by Alan Moore in his run of the Marvel UK comic Captain Britain.

Fans originally thought that the number 616 was a reference of the release date of the first Fantastic Four comic. However Alan Moore when asked about it said that 616 was just a random number of no significance chosen because people always seemed to be talking about 'earth 2' or 'earth 4' but never any higher numbers.

Other Notable Universes

• Earth-295: Age of Apocalypse.
  

• Earth-311: 1602
  

• Earth-555: Reality where the New Universe relaunch (newuniversal) takes place.

• Earth-712: Earth-S, home of the Squadron Supreme.

• Earth-811: Days of Future Past

• Earth-928: Marvel 2099 universe.
  

• Earth-982: Spider-Girl's universe. Also known as MC2

• Earth-1298: Mutant X universe.

• Earth-1610: the Ultimate Universe.

• Earth-2149: Marvel Zombies universe.
  

• Earth-2301: Marvel Mangaverse.
  

• Earth-4935: Askani Earth
  

• Earth-9200: Dystopia. Home reality of Maestro.

• Earth-9997: Earth X

• Earth-15104: Here Comes Tomorrow.

• Earth-31916: Supremeverse, alternate Squadron Supreme.

• Earth-58163: House of M

• Earth-148611: New Universe

Characters/Places that take place outside of the numbered realm:

The Exiles operates in and outside of any universe. Their crystal palace, the Panoptichron is said to exist outside of time and space.

Mojoverse. It was indicated in the Exiles that the Mojoverse and all of its native inhabitants are unique, and unlike all other known universes there are no alternate counterparts.

Characters

A list of characters on Earth-616 originating from other realities.

• Ahab - Earth 811 (Days of Future Past)

• Albion - unnamed reality

• Bishop - Earth-1191

• Blaquesmith - Earth-4935

• Captain UK - Earth-238

• Dark Beast - Earth-295 (Age of Apocalypse)

• Deathlok (Luther Manning) - Earth-7484

• Fury - Earth-238

• Genesis - Earth-4935

• Halloween Jack - Earth-928 (2099 universe)

• Holocaust - Earth-295 (Age of Apocalypse)

• Howard The Duck - unnamed reality

• Longshot - Mojoverse, Longshot has been a member of the X-Men of Earth-616.
  

• Magus - Earth-7528

• Marvel Girl - Earth 811 (Days of Future Past)

• Maxam - Earth-93112

• Nimrod - Earth 811 (Days of Future Past)

• Nocturne - unnamed reality

• Noh-Varr - unnamed reality

• Sat-Yr-9 - Earth 839

• Shadow-X - unnamed reality

• Shard - Earth-1191

• Shatterstar - Mojoworld

• Sugar Man - Earth-295 (Age of Apocalypse)

• Sunpyre - unnamed reality.

• Swordsman (Philiph Jarvert) - Earth-921

• Terror Inc - Earth-88194 (Shadowline)

• Thundra - Earth-715

• Trevor Fitzroy - Earth-1191

• Vision - Earth-6311 (The current Vision's body is from Earth-6311)

• X-Man - Earth-295 (Age of Apocalypse)

Also notable:

• Cable, though born on Earth-616 he was sent as an infant to Earth-4935 and later returned to Earth-616.

• Hobgoblin 2211 - Earth-9500, has been on Earth-616 several times.

• Kang - Earth-6311, Kang has often been on Earth-616 and tried to meddle.

• Korvac - Earth-691

• Kylun - Grew up on Earth-148.

• Spider-Man 2211 - Earth-9500, has been on Earth-616 several times.

• Stryfe - Earth-4935