Aoki Lee Simmons has already called it quits with her much older boyfriend ... TMZ has confirmed.
The exact reason for their split remains unclear -- but we're told Aoki isn't planning on dating restaurateur Vittorio Assaf beyond the time they've already spent together in St. Barts ... where they've been canoodling for the past several days.
While we know Russell was supportive of the relationship -- People Mag reports that Aoki's mom was not approving at all ... in fact, they say KLS was "concerned" about the age gap.
Aoki herself also seemed to scoff at the haters in some since-deleted social posts, where she was referring to Vittorio with pet names, but with their split -- first reported by Page Six -- this ain't going anywhere.
Just as fast as the news came, it's fizzled out -- remember, it was just last week when news broke Aoki was hooking up with Vittorio after PDA-packed vacation photos of them from St. Barts emerged.
The photos went viral instantly ... and the general consensus was ... creepy.
Like we said, RS himself wasn't sweating it -- telling us Aoki had given him a heads up this would be coming out, and saying he "wasn't gonna kick and scream about her choices."
As for Aoki, she hasn't directly addressed all the dating uproar herself yet ... but we do know she's moving on. Spring fling, as they say.