Cooper Flagg is reaping the benefits of being the (super likely) No. 1 overall pick -- the former Duke star is BOSS' newest ambassador ... and is commemorating the deal by repping the brand at the NBA Draft!!
All eyes will be on Flagg at the Barclays Center on Wednesday ... with his name expected to be called when the Dallas Mavericks submit their selection in a matter of hours.
Launch Gallery Launch Gallery GettyTMZ Sports has learned Flagg -- the National College Player of the Year -- chose to keep it slick and smooth with an Italian three-piece stretch wool suit by BOSS, along with a slim-fit shirt and Italian-made silk jacquard tie.