Thibaut Pinot, the youngest rider in the Tour de France, presented the French with their first stage victory in this year's edition after winning the hilly 157.5 kms Belfort-Porrentruy eighth stage on Sunday.
The 22-year-old, born near Belfort, attacked in the last of seven climbs to cross the line on his own.
Pinot finished 26 seconds ahead of a group that included a host of Tour favourites, leaving defending champion Cadel Evans in second place and Frenchman Tony Gallop in third.
British rider Bradley Wiggins retained the yellow jersey after finishing fourth.
Pinot, who was not even selected in the initial choice of Tour riders for his FDJ-BigMatteam, was in buoyant mood afterwards.
"It'sa dream. I rode the longest last 10 kilometres of my life," he said.
"Iinsisted I do it, because I knew what I could do. I hope my team director has no regrets now."
Monday's ninth stage, a 41.5-kilometres individual time trial between Arc-et-Senansand Besancon, is another key moment of the Tour, with Wiggins expected to tighten his grip on that yellow jersey.
Photograph: Bogdan Cristel/Reuters