Vienna, August 3: Formula One great Niki Lauda underwent lung transplant surgery in Austria on Thursday (August 2).
"Due to a severe lung disease Niki Lauda had to undergo a lung transplantation at the AKH Vienna today," Vienna General Hospital said in a statement on its website.
"We ask for your understanding that the family will not make any public statements and request the privacy of the Lauda family."
Lauda, 69, won the first of three F1 world championships with Ferrari in 1975.
The Austrian suffered severe burns and was close to death after a fiery crash during the German Grand Prix at the Nurburgring a year later, but recovered and remarkably was back racing just six weeks later, finishing second behind James Hunt in the battle for the 1976 drivers' crown.
Lauda won the championship again with Ferrari in 1977 and retired in 1979, returning to the sport in 1982 and winning his third and final title at McLaren in 1984.
He has served as non-executive chairman of Mercedes' F1 team since 2012, signing a new four-year contract in 2017.
The Silver Arrows have won the last four drivers' and constructors' world championships.