Depends whether you're asking about the earliest myth we can posit based on later evidence, or the earliest attestation of a creation myth: for more specifics you might want to clarify which you're after.

For the record, here's an earlier thread, with an answer by u/Algernon_Asimov that addresses the first interpretation, and one by me that focuses on the second. I'd be delighted if someone could add some more really early stuff that we forgot there!

Edit: clarification as per flapanther33781's post below (thanks).