Himitsu-san! I has a Q 4 U! I understand that Ultraman has several timelines and continuities within the franchise. Would you mind shedding some light on which series belong to what continuity?
Let me start by saying thanks for the question! Also, oh boy is this one a weird one. I would also say I am still learning about the history of Ultraman so my answer might not be entirely correct. Due to the complexity involved here, I am only going to cover the main, live-action, Japanese produced series here. Sorry fans of Ultraman Powered, Ultraman Great and Ultraman USA, they won’t be counted here.
Let’s start with the main continuity, the one that’s the core of all the others. That would be the Showa series continuity, also known as the M78 Continuity because that is where most of the heroes from this series of shows hail from and where the main Space Garrison base is located.
The M78 Continuity started in 1966 with Ultraman.
It was never really intended to be the launching point for a franchise and the followup series Ultraseven wasn’t originally in the same continuity as Ultraman.
However, come 1971, the series The Return of Ultraman introduced not only a new hero (retroactively) known as Ultraman Jack but established that Ultraseven and Ultraman were in the same universe as this new hero.
From there this continuity took off and soon Ultraman Ace, Ultraman Taro, Ultraman Leo and Ultraman 80 were all part of one big continuity family.
Now, for the rest of the M78 Continuity we need to skip ahead 26 years from 1980 to 2006 when a new member of this extended family was introduced, Ultraman Mebius. He was also part of this universe, a young new hero who joined the rest.
After him came a few movies starring yet another new hero, Ultraman Zero, the son of Ultraseven. We’ll get back to him in a bit though.
In that 26 year gap, there were several all new continuities that sprung up. This started in 1996 with Ultraman Tiga.
Tiga was an all-new hero with an origin utterly divorced from the previous universe’s giants from the Land of Light. However, he would not be alone in his little corner of reality as the next series, Ultraman Dyna was also set in his timeline!
So, when the series after that was announced, we found out it would not share a universe with Tiga and Dyna but be set in yet another new continuity. This series was Ultraman Gaia.
After Gaia, there were a series of stand alone continuities starting with Ultraman Neos in 2000.
Then came Ultraman Cosmos in 2002!
By this point Ultraman was starting to appeal way more to children than adults so another new continuity, this one skewed towards an older audience was created. This was the continuity that Ultraman Nexus was set within.
Then in 2005, there was yet another series outside the continuity of all of the others, Ultraman Max!
That brings us back to Ultraman Mebius and the M78 continuity and we can finally talk about Ultraman Zero. Zero did something new and revolutionary for the Ultra series, it introduced the concept of the multiverse. Zero finds himself between universes, staring at the vastness of literal infinity with all the possible universes laid out before him, floating in separate bubbles.
That’s when the universe hopping began and that’s why in series like Ultraman Ginga, Ultraman X and Ultraman Orb we get heroes from ALL of the continuities popping up.
So, there are a bunch of continuities, the main one is the M78 Continuity but thanks to the multiverse and the discovery of relatively easy travel within it, all the universes can now interact.
I think I need to go lie down now.