Kim Kardashian has added another superstar athlete to her SKIMS roster -- this time, it's Cleveland Cavaliers hooper Donovan Mitchell ... who fully committed to being a new undies model!!
Spida got half-naked for a locker room-themed photo shoot for the brand's new campaign ... just a few days before the NBA season kicks off on Oct. 22.
28-year-old Mitchell sported several different Cotton and Stretch undies from Kardashian's line ... and not only did he look good showing off his athletic bod -- he said he felt good in them, too.