Zion Williamson is about to be an instant millionaire ... and who better than "Shark Tank" star and wealthy businessman Kevin O'Leary to give the future NBA superstar some investment advice!!!

So grab a pen and paper, Zion ... 'cause Mr. Wonderful is about to give you a crash course in being rich AF.

-- Hire an advisor to handle all the boring stuff ... "over time, build a real estate portfolio, some really boring bonds and some large cap to the pink stocks." ... whatever that means.

-- NO ENTOURAGE ... sorry, Drama and Turtle -- O'Leary says it's better to keep your circles small ..."Walk around with 2 people, not 20. Most of the money goes to people you forget after a while ... support your mother, not your friends!!"