TMZ Sports talked to the UFC honcho just days before UFC 268 ... headlined by Usman vs. Covington, a rematch of their incredible 2019 scrap -- a fight Kamaru won via 5th round knockout.

"Usman is in a place right now where he's the pound-for-pound best fighter in the world. He's arguably right now the greatest welterweight of all time. He's already lapping guys, he's coming back and fighting guys for a second time," White said of Usman's legacy.

A few of the career attributes Dana listed ... undefeated in the UFC (14-0), won The Ultimate Fighter, longest win streak in welterweight history, least time on the bottom in UFC history, highest takedown defense in UFC history, to name a few.

And, Dana believes Usman could actually go down as the greatest MMA fighter ever.

"Colby Covington is a badass. He's very, very good. And, Usman beating him again will probably solidify him as the greatest welterweight ever, and yes, creeping up on G.O.A.T. status."

But, in order to do that, Kamaru must first beat Colby, the #1 contender, at UFC 268 Saturday night.