Ric Flair is opening up about his past struggles with alcoholism ... admitting that he consumed the equivalent of "20 DRINKS A DAY" during his legendary pro wrestling career.

The Nature Boy talked about his wild ways Thursday on "The Dan Le Batard Show" ... and how they nearly cost him his life.

"I just drank too much," Flair said. "Between 3,700 and 4,000 calories worth of booze ... in my body every day. Like 20 drinks a day."

Ric's alcohol abuse eventually caught up to him ... he says he was on life support for 10 days after having emergency surgery last month, and doctors didn't know whether or not he'd make it.

Good news, though -- Naitch says he's kickin' booze to the curb so he can have a long, healthy life.

WOOOOO!!