The first written fictional work we know of is the Epic of Gilgamesh from ~4000years ago. Considering that many societies, including those with writing also had strong oral traditions and these likely included fictional stories. A lot of these stories include fictional settings, such as heaven or hell/netherworld. Thus the first fictional universes can be considered as prior to writing.

I'd expect some pantheon of gods would fit the definition.
The Epic of Gilgamesh is a collection of stories with likely different authors. That might fit what you're looking for. As far as I know it's the oldest written stories we have, some 5000 years old. And it's about a superhero believe it or not.

Have you ever read the Illiad or the Odyssey?

Oh my god both. I hate them so much because how homer get's a pass for his writing style. Instead of saying a rose on a mountain. It's, there was this very bright red rose on top of a mountain surrounded by snow and the light from the snow glistened on the rose itself almost saying good morning. It's that filler crap I have a problem with. Yes I may nitpick but man it drives me up the wall cause I was forced to memorize both for history and English. I FUCKING HATE HOMERIC EPICS (not the stories just the style he suposedly invented)

The Illiad and The Odyssey maybe? And you can add The Aeneid to it as well. It depends a bit on how you define a fictional universe, but this is a shared universe with 3 protagonists : Achilles, Odysseus and Aeneas.

same writer? But do they share the area like they live in or something like L and O and SVU and Chicago shows? no challenging you or anything but my bro is big on the "universe" stuff and thought it would stop his craving for a little bit to get the original shared universe. Thank for you reply by the way. Have a happy fourth. He's absolutely loves Elmore Leonard for example.

The Illiad and The Odyssey are both attributed to Homer, while The Aeneid is written much later by Virgil.

The Illiad is about the Trojan war, while The Odyssey follows the greek Odysseus who returns from the Trojan war and The Aeneid follows the Trojan Aeneas who flees the destruction of Troy and tries to find a new home for the Trojans.

Do the ancient epics really count? Many were not viewed as fiction in their time.

Not to get into a debate. But back then did they view the likes of Oddyseus and Achilles like we do Jesus? Through word of mouth and just belief with no credible fact? Oh Happy 4th this weekend. Sure they can't. But were they written that way in the first place like the MCU was or was it just a coincedence?

I would asume the Aeneid was viewed as fiction.Wasn't it comissioned by Augustus to make up a story how the romans are Descendants of the troyan folks?
I think some legends about Aeneas were adapted by the Romans earlier.

Word of mouth was likely valued differently than it is by us. We may look down on it, but word of mouth was/is the trusted means of passing on knowledge for many cultures, even when writing was an option. And it can be accurate through the ages.

Aboriginals in Tasmania have oral traditions dating back to when it was connected to Australia. 12,000 years ago. Or oral records of hunting grounds dating back to the Ice Age that are now under water.

Both Achilles and Odysseus have had their own religious devotions through the ages. And whether you believe or not, they're still a bit different than something that was published explicitly as fiction.

Sherlock Holmes had a developed canon.

I hate them so much because how homer get’s a pass for his writing style.

You realize that Homer didn’t write in English? Your beef is more with the translator here.