Champion sailor Florence Arthaud, Olympic gold medallist swimmer Camille Muffat and Olympic boxer Alexis Vastine were among 10 killed when two helicopters filming the survival series "Dropped" smashed into each other in the rugged mountains of La Rioja province, local officials said.
"The whole of France is in mourning," said Prime Minister Manuel Valls.
Rioja provincial spokesman Horacio Alarcon told AFP there were no survivors in the crash, which happened in good weather conditions yesterday.
Local media showed the wreckage of the two helicopters in flames on the dry scrubland in the northwestern Argentinian province.
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It was the worst accident in the history of reality television.
Alongside the three sports stars, five French TV crew members and two Argentine pilots died in the crash, a police source said.
Arthaud, 57, was considered one of the best sailors in the world, a woman who conquered what had been a strictly male-dominated sport. Her titles included the 1990 Route du Rhum, the most prestigious race to cross the Atlantic solo.
Muffat, 25, was one of the top swimmers in French history, winning three medals at the London Olympics in 2012, including gold in the 400-metres freestyle.
She shocked the sporting world in June 2014 by announcing her sudden retirement at the age of 24, exhausted by the long hours of training in the pool.
Vastine, 28, won a bronze medal at the Beijing games in 2008 in the light welterweight category.
President Francois Hollande led the tributes, saying the "brutal death of our compatriots is an immense sadness."
"They died because, again, they wanted to push the boundaries," said Hollande.