Robert Downey Jr.'s Gum From Jon Favreau Walk of Fame Hits eBay for $55k

Robert Downey Jr. fans now have a shot at an interesting piece of history from Jon Favreau's Walk of Fame ceremony ... cause a guy is selling what he claims is Iron Man's chewed-up gum!!!

The gum is currently up for sale on eBay and it has a starting bid of $55,000. According to the listing, the seller attended the ceremony where actor/producer and "Iron Man" director Jon Favreau was added to the Hollywood Walk of Fame.

Iron Man himself, RDJ, was on hand for the big event ... and created a moment by taking chewed gum out of his mouth and sticking on Jon's shiny new star. Downey joked it was "just to make it official."

The seller claims he was able to snag the gum, right where RDJ left it. Now, it's apparently up for grabs "in the same condition" he got it 😬

We know what you're thinking ... how in the hell's he gonna authenticate???

Well, the seller is super confident it's the real deal, and says the buyer can even test the gum for RDJ's DNA. Good luck getting Robert to provide a sample for comparison, though.

If used celeb gum is your thing, bidding ends Friday! Also ... ew.