Nate Robinson -- a three-time NBA slam dunk champion -- announced he's been battling kidney failure for four years ... and is undergoing treatment.
Robinson shared the news on Saturday, saying, "I am currently undergoing treatment for Renal Kidney Failure and have been privately dealing with it for the last four years."
He continued ... "I'm sharing this now because I want to be the voice for all those who are having trouble speaking about this illness and come together for a greater cause -- our health."
Robinson, 38, was selected in the first round of the 2005 NBA draft by the Phoenix Suns .