Niki Lauda has been released from hospital after contracting influenza.
The three-time Formula One world champion was admitted earlier in January, just five months after a lung transplant.
A spokesperson from Vienna General Hospital, where Lauda had been receiving treatment, confirmed the 69-year-old had left the facility.
Lauda underwent a life-saving operation in August, and was released for rehabilitation nearly four months later before falling ill with flu while on holiday in Ibiza.
He has been in his role as Mercedes' non-executive chairman since 2012 but his poor health meant he missed the second half of last season.
Mercedes staff paid tribute to Lauda at their Northamptonshire factory while celebrating both the team and Lewis Hamilton's championship honours by wearing red caps similar to the one usually sported by the Austrian.
Lauda, who survived a fireball inferno at the 1976 German Grand Prix, won his three titles in 1975, 1977 and 1984.
