Formula 1 world champion Niki Lauda has died at the age of 70.
The Austrian had been fighting health issues since the middle of last year, including a lung transplant in August which needed to wait two months in hospital.
He was then admitted to hospital again for a short period in early 2019 following contracting a flu infection.
There have been reports from the Austrian press in recent days that he has been receiving renal dialysis in Switzerland.
He has now been confirmed that he has surrendered to his illness, dying on Monday to be surrounded by family.
"With deep sadness, we announced that our beloved Niki has died quietly with his family on Monday," his family said in a statement given to Austrian media.
"His unique achievements as an athlete and entrepreneur remain unforgettable, his relentless love for action, his simplicity and his courage continue.
"It was a role model and a benchmark for all of us, he was a loving and caring husband, father and grandfather away from the public, and will be lost."
Lauda was a giant of Formula 1 paddock for over four decades.
He made his first appearance in 1971, winning his first race in 1974 after joining Ferrari, and then claimed first title in 1975.
The following season he was fortunate to survive a fiery accident at the Nurburgring which left him badly burned.
Surprisingly, only two races lost, making one of the most amazing things in sporting history, and only one point for James Hunt, McLaren, who denied him the championship.
His second title came to Ferrari in 1977, before Lauda moved to Brabham for the 1978 season.
His stay there lasted less than two seasons that Lauda retired from F1 halfway through rehearsal for the 1979 Grand Prix.
He then concentrated on his active air charter business in Austria until 1982, when he returned F1 with McLaren.
That relationship gave a two-season championship later in the world, when his fellow Alain Prost beat only half a point.
Following his second retirement in 1985, Lauda took on the role of consultant manager at Ferrari in the 1990s, which was followed by the team's main post in Jaguar in 2001 – although it only lasted a year.
In 2012 he became a non-executive chairman of the Mercedes F1 team, and was a key figure in the squad who won many titles until his illness last year.