De Gendt, who rides for Lotto Soudal, triumphed in a time of 5 hours 17sec on the 200 kilometres route from Mâcon to Saint-Étienne.

His winning margin over Frenchman Thibaut Pinot of Groupama-FDJ was six seconds with Deceuninck-QuickStep’s Alaphilippe coming home in the same time as his compatriot.

"From 70km to go, I just kept riding full gas until last climb," De Gendt, whose only previous Tour de France stage win came in 2016, said.

"The bunch was coming closer but I had to go solo and stay ahead of them. 

"I had really good feelings all day."

Defending champion Geraint Thomas of Great Britain recovered from a crash with 17km remaining to finish among the 32 riders that were 26 seconds adrift, including his main rivals.

Alaphilippe has retaken the general classification lead from Italy’s Giulio Ciccone.

He had lost it to the Trek-Segafredo rider after stage six.

The overall leading time stands at 34:17:59.

Ciccone is 23 seconds behind in second, while Pinot is 53 seconds off the pace in third.

New Zealand’s George Bennett of Team Jumbo-Visma occupies fourth spot.

He trails Alaphilippe by 1:10, with Team Ineos' Thomas a further two seconds back.

Stage nine is due to take place tomorrow.

It is a 170.5km route from Saint-Étienne to Brioude.

The 21-stage event is scheduled to conclude on July 28.