The seven-time All-Star center said Thursday he won't return from a devastating leg injury Dec. 19, 2007 -- the fourth anniversary of his lifesaving kidney transplant. He had been working out at the Miami Heat complex and said he's running and jumping again, but he feared another leg injury if he returned.
"My health is more important than anything," Mourning said at a news conference. "God willing I'll be able to live another 40 or 50 years, and I want to do it in a comfortable state. Right now I'm there."
Mourning, who turns 39 next month, played at Georgetown and was the second overall pick in the 1992 draft by the Charlotte Hornets. He also played for New Jersey but spent the majority of his career with the Heat, helping them reach the playoffs six consecutive years. He was the backup center to Shaquille O'Neal when Miami won the NBA title in 2006.
If he hadn't won a championship ring, Mourning said he might keep playing.
"When you've got something you love and you're passionate about, it's hard to let that go," Mourning said. "But at 38 I feel I've physically done all I can for this game. It has been an amazing ride."
Mourning was diagnosed in October 2000 with focal segmental glomerulosclerosis, a career-threatening kidney disease. He missed most of the ensuing season but rejoined the Heat in March 2001 and made the All-Star team the following year.
When his condition worsened, he missed the entire 2002-03 season and underwent a transplant in 2003. Again he returned, but for three consecutive summers beginning in 2005, Mourning considered retirement before choosing to keep playing.
He hasn't played since tearing the patella tendon and quadriceps muscle in his right leg 13 months ago.
"It's not a sad day, but it's a day to celebrate," Mourning said. "I can think of a million people right now that would have loved to walk the path I've walked. The ups and the downs made it even more joyous."
"He was the very best thing that ever happened to this franchise," Riley said. "He will always be respected by Mickey and myself for being the taproot of a culture that we're really proud of. He embodies that.
"We love you, Zo. You will wear that jersey one more time -- when we rip it off your back and hang it from the rafters."
Mourning was in the Heat locker room before Wednesday's game against Boston and told former teammates Dwyane Wade and Udonis Haslem he planned to retire.
"We've lost him as a basketball player, but he's still going to be around," Wade said. "He's still what Miami Heat basketball is all about. For any player who comes here, Alonzo is always going to be the mirror image of what you would like to be."
In 15 seasons, Mourning averaged 17.1 points and 8.5 rebounds and twice was chosen NBA defensive player of the year. He averaged 6.0 points and 3.7 rebounds in 25 games last season for the Heat.
Mourning said he and his family will remain in Miami, where he has long supported charitable causes and campaigned for better education. He attended President Barack Obama's inauguration on Tuesday.
Tributes from around the league started as news trickled out that Mourning was retiring.
"He was a guy who played as hard as anybody who's ever played in this league," Van Gundy said. "I mean, night in and night out, he's one of the fiercest competitors and hardest-playing guys who's ever been in the league."
Van Gundy, who was with the Heat as an assistant when Mourning was at the peak of his career, said if Mourning is ready for the next phase of his life, then retiring would be the right call.
"As long as he's at peace with it either way, I'll be happy for him," Van Gundy said.