Double Olympic champion Hicham El Guerrouj has announced his retirement.
Ending his career was an emotional moment for El Guerrouj
The Moroccan, the 1500m world record holder, claimed a brilliant 1500m and 5,000m double at the Athens Games to add to his four 1500m world titles.
But the man thought to be the greatest 1500m runner of all time has not raced since Athens because of injury.
At a news conference, a tearful El Guerrouj described his decision as "historic and difficult", saying he was crying out of "joy and not sadness".
El Guerrouj said he had not slept well since winning his double gold in Athens.
"I took the decision to retire because I suddenly began to sleep well three weeks ago," he said.
"During this period I was in a state of flux, I just did not know whether I should run or stop. Now it is done, I am relieved."
"I have no willingness or motivation to continue competing. I am quitting racing to spend more time with my family and focus on my business.
"For 16 years, I've done sports. Now I want to start a new life. I will return to another world whose horizons I do not know."
A back injury forced the 31-year-old out of this year's World Indoor Championships in Moscow.
El Guerrouj also left it late before deciding to withdraw from the 2005 Worlds because of a virus. He then declared he would take the rest of the year off before racing a farewell season in 2006.
The "King of the Mile" felt he had nothing left to achieve after his historic double triumph in Athens.
El Guerrouj became the first man since Finnish legend Paavo Nurmi in 1924 to complete the 1500m-5,000m double.
EL GUERROUJ FACTS
Born: 14 September 1974
1500m - 3:26.00mins (WR)
5,000m - 12:50.24mins
World Athletics medals:
2003 - 1500m gold, 5,000m silver
2001 - 1500m gold
1999 - 1500m gold
1997 - 1500m gold
1995 - 1500m silver
2004 - 1500m gold, 5,000m gold
2000 Olympics - 1500m silver
World Indoor medals:
1995 - 1500m gold
1997 - 1500m gold
2001 - 3,000m gold
But it did not come easily as he was forced to out-sprint world record holder Kenenisa Bekele in the final few metres of the 5,000m just days after fending off Bernard Lagat to claim the 1500m title.
El Guerrouj's Greek triumphs made amends for his disastrous previous Olympic campaigns.
At the 1996 Games in Atlanta he tripped on the final lap of the 1500m final to finish last.
Four years later in Sydney, a poor tactical race saw him surrender the gold to Kenya's Noah Ngeny and break down in tears on the track.
El Guerrouj's dominance of the 1500m saw him notch up four consecutive world titles in 1997, 1999, 2001 and 2003.
His world record time of three minutes 26 seconds, which he set eight years ago in Rome, still stands.
The Moroccan also holds the mile record (3:43.13) as well as the 2,000m, indoor 1500m and mile marks.
Away from the track, El Guerrouj is a representative for the International Association of Athletics Federations (IAAF), Unicef and the International Olympic Committee.