Milen Dobrev, a weightlifting gold medallist at the 2004 OlympicGames, has been found dead at his home, aged 35.
Dobrev triumphed in the 94kg category in Athens.
He also claimed gold at the 2003 world championships and won two European titles before retiring in 2008.
"I can't stop crying," Bulgaria's former weightlifting coach Plamen Asparuhov said. "He was the best person I ever knew."
A Bulgarian interior ministry spokesperson said: "Dobrev's body was found at his home. There are no signs of violence and the cause of death is still not clear."
Bulgarian weightlifters have won 11 Olympic titles since 1972, making it one the most successful sports in the Balkan country.