Insane Conor, Floyd, Giannis, Messi & Ronaldo Autograph Card Hits Auction

One of the most INSANE cards ever created -- featuring signatures from eight sports legends including Conor McGregor and Floyd Mayweather -- has just hit the auction block, and it could sell for the price of a brand-new car!!

The piece is wild -- it's got autographs from McGregor, Mayweather, Giannis Antetokounmpo, Steph Curry, Errol Spence Jr., Lionel Messi, Cristiano Ronaldo and Chloe Kim on it ... and Leaf Trading Cards says it's the only one of its kind ever created.

TMZ Sports has learned bidding on the card at Goldin Auctions just began this week -- and we're told the expectation is for it to ultimately sell later this month for somewhere around $20,000!!

And, given the names on the piece -- and how Giannis' star has absolutely exploded this summer -- seems like a pretty great price to us.

As for how the card was obtained ... we're told someone actually pulled it in a box break -- which, yeah, talk about great luck.

The card was given an 8 grade by Beckett ... with a perfect 10 for its sharp corners.