Floyd Mayweather -- $50 Mil Offer to McGregor ... But No Deal Yet

Floyd Mayweather has a $50 MILLION offer out to Conor McGregor, sources tell TMZ Sports ... but it's going to take a lot more to seal the deal.

We're told Floyd is proposing a New Year's Eve fight in Vegas and Conor is game. We're told Floyd's $50 million offer is far less than half the amount the fight would rake in ... and therein lies the rub.

Floyd has been talking to the wrong guy, because Conor can't ink the deal. It's all about convincing Dana White, and there's just no way White would accept such a lopsided deal. Fact is ... in 3 critical Pay-Per-View markets -- Europe, Australia and Canada -- Conor is a bigger star than Floyd.

Floyd's last fight produced disappointing PPV numbers, and Conor's star has never been brighter. Even his loss to Nate Diaz was epic ... the fight was great and it did not disappoint fans.

Sources connected with Floyd tell us ... the champ has not approached Dana, at least not yet.  

Open your wallet Mayweather ... it could happen.