Kobe Bryant made the announcement in a post on The Players' Tribune on Sunday afternoon.
"My heart can take the pounding. My mind can handle the grind. But my body knows it's time to say goodbye," Bryant wrote. "And that's OK. I'm ready to let you go. I want you to know now. So we both can savor every moment we have left together. The good and the bad. We have given each other all that we have."
Here's some reactions to the news from around the league:
NBA Commissioner Adam Silver: "Kobe Bryant is one of the greatest players in the history of our game.