Poland's Katarzyna Niewiadoma won her first women's Tour de France title by just four seconds on Sunday as she dug in during the race's gruelling final Alpine ascent.

The 29-year-old Canyon SRAM rider summited the daunting Alpe d'Huez mountain one minute one second behind stage winner Demi Vollering to maintain her grip on the yellow jersey.

"It's so crazy to be honest, the whole stage was such a crazy rollercoaster," said a visibly emotional Niewiadoma.

"I've gone through such a terrible time on this climb, like I hated everything, then to arriving at the finish line and learning that I won Tour de France, which is insane. It's so mind-blowing."

The Tour was turned upside down on Thursday during the fifth stage when Vollering was caught up in a huge crash six kilometres from the finish in Amneville, losing 1min 47sec on the leader.

After third-placed finishes in the previous two Tours and a disappointing eighth-place finish at the 2024 Olympic Games road race, the victory tasted even sweeter for Niewiadoma.

"I think last year's third place was there to reward me with this victory and same as two weeks ago I was so disappointed getting stuck behind a crash during the Olympics," said the Limanowa-native.

"I feel like during this week, all the stars aligned for my team and for myself." (AFP)