LeBron James is getting the highest possible praise from Muhammad Ali's ex-wife -- who's anointed the NBA star the "Muhammad Ali of basketball" for the way he's addressed racism in America. 

Khalilah Ali -- who was married to Muhammad from '67 to '76 and has 4 kids with the boxing legend -- tells TMZ Sports she was extremely impressed with Bron's reaction to the racist vandalism at his L.A. home.

She says Muhammad would not only be proud ... he'd be a huge fan.

"I think Ali would be very supportive of him because Ali went through the same thing in the past," Khalilah says.

"He would really look up to James."