Dana White On Mayweather vs. McGregor ... 'There Is No Deal'

Dana White tells TMZ Sports plain and simple ... when it comes to the Floyd Mayweather vs. Conor McGregor fight, "There is no deal."

There was a report out of Ireland that Conor and Floyd have agreed on terms for a megafight -- but it hasn't been formally signed because of a "holdup" from an unnamed 3rd party.

The UFC boss didn't get into specifics ... only saying point-blank, "No deal."

White has previously told us the chances of the fight coming to fruition are small -- and earlier this month told us negotiations were not going well.

Then again, anything's possible.