"My body knows it's time to say goodbye" he wrote in a first-person story titled "Dear Basketball" published on The Players' Tribune website.
The 37-year-old has scored 32,683 points, though in recent seasons his form has been hindered by injury.
Kobe was the bridge from the Jordan era to the likes of LeBron, Durant and Curry, imparting the lessons of His Airness to the next generation of stars.
The formality of Bryant announcing this season will be his last sent ticket prices skyrocketing Sunday night.
"Within 10 minutes of Kobe's announcement, we had thousands of inquiries and sales," said Harris Rosner, owner of Los Angeles-based VIP Tickets.