Soon after news of the accident on Sunday afternoon, Martin Brundle, who was Schumacher's team-mate at Benetton in 1992 and 1993, tweeted: "Let's hope Michael Schumacher's ski shunt is not too bad and that he's totally fixable. He's a crazy brave skydiving/bike racing daredevil."
Hours later, when the full extent of Schumacher's injuries had become clear, he urged: "Come on Michael, give us one of those race stints at pure qualifying pace to win through, like you used to. You can do it."
Felipe Massa, the Brazilian driver whose injury brought Schumacher back to F1 in 2009, posted a picture of the pair embracing on Instragram, with the Portuguese message: "I'm praying for God to protect you, brother!"
In English, he wrote: ""I hope you have a quick recovery! God bless you, Michael!"
Schumacher returned to the sport to cover for Massa while he was having a titanium plate put in his skull after crashing in the Hungarian Grand Prix.
Jean-Eric Vergne, Jules Bianchi, and Max Chilton also weighed in, offering best wishes and wishing him a quick recovery.
Romain Grosjean, who finished second to the German legend in the 2012 Nations' Cup, tweeted: "All our thoughts to Schumi and his family. Heikki Kovalainen, who tussled with him on the track in 2004 and 2007, wished him a "full recovery soon". Both gave him the hashtag "#legend".
Stars from other sports also added their well wishes. Retired cricketer Michael Vaughan said: "Forget the cricket. Everyone's thoughts should be with Michael Schumacher."
Scottish F1 driver Paul di Resta tweeted: "Terrible news about MSC, thinking of him and his family. Hoping for better news and that he can pull through #getwellsoon."
Former F1 driver Giancarlo Fisichella tweeted: "I know you Michael, you are the man, you are the best you are..... This is the most difficult race but I am sure you we will again!"
Golfer Ian Poulter wrote: "Really hoping Michael Schumacher comes thru his terrible skiing accident. Wishing him well."
German international footballer Jerome Boateng tweeted: "Get well soon, Michael Schumacher!"
Olympic rowing champion Sir Michael Pinsent wrote: "Come on Michael Schumacher - thinking positive thoughts for him."