Vincenzo Pinto/AFP
A picture taken on January 17, 2003 shows Formula One World champion Michael Schumacher holding his skis before a giant slalom race in Madonna di Campiglio
The 44-year-old German was "suffering a serious brain trauma with coma on his arrival, which required an immediate neurosurgical operation", the hospital in the southeast French city of Grenoble said in a statement.
"He remains in a critical condition."
Schumacher had been skiing off-piste in the upmarket Meribel resort, where he reportedly has a property, when he fell and hit his head on a rock, mountain police who gave him first aid said.
He was airlifted to a local hospital, then to the Grenoble facility. A specialist neurosurgeon from Paris was rushed in to oversee his treatment.
The director of the Meribel resort, Christophe Gernigon-Lecomte, had said just after the accident that Schumacher had been wearing a helmet and was "conscious but a little agitated" just after the accident, suggesting he had not received life-threatening injuries.
But when Schumacher then fell into coma, doctors realised the damage was worse than initially feared.
The two mountain police officers who gave first aid said Schumacher was suffering "severe cranial trauma" when they got to him and a helicopter was brought in to evacuate him within 10 minutes.
A renowned Paris neurosurgeon, doctor Gerard Saillant, was brought to the Grenoble hospital in a police car to take charge of the famous patient.
The hospital statement was signed by the facility's neurosurgeon, the professor in charge of its anaesthesia/revival unit, and the hospital's deputy director.
Schumacher was on a private stay in Meribel, according to his spokeswoman. He is to have his 45th birthday next Friday.
A towering figure in Formula One
Schumacher, who won the last of his world titles in 2004, definitively retired in 2012 in the Brazilian Grand Prix, in which he finished seventh, after an abandoned attempt to quit six years earlier.
Since his debut in 1991, the German towered over the sport, winning more Formula One world titles and races than any other. He had a record 91 wins and is one of only two men to reach 300 grands prix.
Schumacher's duels in his heyday with Damon Hill and Jacques Villeneuve, fired by an unquenchable competitive spirit, have gone down in Formula One lore.
Schumacher was born in January 1969 near Cologne, Germany, the son of a bricklayer who also ran the local go-kart track, where his mother worked in the canteen.
By 1987, Schumacher was the German and European go-kart champion and was soon racing professionally. In 1991 he burst into Formula One by qualifying seventh in his debut race in Belgium and a year later he was racing for Benetton, where he won his first Formula One grand prix in 1992.
After joining Ferrari in 1996, Schumacher achieved infamy by trying to ram Villeneuve off the road at Jerez in the last race of 1997, and was disqualified from the championship as punishment.
Over the next decade, he went from strength to strength, dominating the podium, before trying to retire the first time aged 37.
But the father of three could not resist the lure of the track and in 2010 he signed a three-year deal with Mercedes.
But slower reflexes and a less competitive car meant Schumacher could not reproduce his former glory and he quit for good in 2012. His helmet had a message for fans: "Life is about passions -- Thank you for sharing mine."
