The 34-year-old died on his way to an athletics meeting in Johannesburg, a statement from the office of South Africa President Jacob Zuma said on Friday.
"The nation has lost a true hero and one of our most disciplined and talented athletes who flew the South African flag across the sporting world," said Zuma.
"We wish to convey, on behalf of the Government and the entire nation, our heartfelt condolences to his family, ASA (Athletics South Africa), the South African sports fraternity and the International Olympic Committee."
Mulaudzi, who carried the South African flag in the opening ceremony at the Athens Olympics in 2004, won his silver medal at the same Games having picked up a Commonwealth gold in Manchester two years earlier.
He won the 2009 world championship title in Berlin after suffering the disappointment of a semi-final exit in the Beijing Olympics a year earlier.
Mulaudzi retired from athletics in 2013.
Ian Harries, his coach between 2000-05, told the national Mail & Guardian newspaper last year: "Though not the South African record holder for his event, he is regarded by many as our greatest 800 metres runner.
"He was very competitive, aggressive and a very tactically aware runner who thrived best over a fast race. He had incredible speed-strength endurance.
"Despite his somewhat shy exterior and being wary of too much media exposure I, personally, think of him as a true legend of the event," added Harries.
(Reporting by Nick Said, editing by Tony Jimenez)
