Team Mitchelton-Scott's South African rider Daryl Impey won stage nine of the Tour de France on Sunday, leaving local fans to settle for Frenchman Julian Alaphilippe keeping hold of the yellow jersey on the Bastille Day.

Impey, wearing his national champion jersey, was part of a mass breakaway that quickly opened a 10-minute gap and extended it throughout the race with the pack eventually trailing in 16 minutes after Impey had beaten Belgian Tiesj Benoot to the line.

Defending champion Geraint Thomas and the other overall title contenders finished together in a low-key finale to the 170km rolling run.

"That was a really tough race. I'm so happy to win on July 14," said a broadly smiling Impey, who crossed the line with both arms aloft, releasing a huge victory cry.

The 2019 Tour Down Under winner and all-rounder won a Tour de France team time-trial back in 2013, and a few days later took the overall lead to become his nation's first yellow jersey holder.

"This is my greatest ever victory, just as good as wearing the yellow jersey, nothing can top this," he said. "It was a tough, solid day."

After a frantic day over seven mountains on Saturday, the stage embarked from the Saint-Etienne soccer stadium in a festive Bastille Day atmosphere with many fans shouting for local man Romain Bardet as well as the yellow jersey wearer Alaphilippe.

"This is a day I'll never forget," said the overall leader.

"All those people shouting my name, it really is something, and my grandfather was there at the finish line, so it was really special," added the former soldier, who came into the race without any aspirations of becoming France's first Tour winner since 1985.