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 grueling 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 roller coaster," said a visibly emotional Niewiadoma.