The Deceuninck-Quick-Step rider rode clear with Denmark's Astana cyclist Jakob Fuglsang with about 15 kilometres to go and raced past his rival late on to win by two seconds.

Alaphilippe, who won the mountains classification at the Tour de France last year, showed great power on the race-ending climb to triumph in 4 hours 47min 14sec.

Wout van Aert of Belgium and Jumbo-Visma had caught the leading pair but he slipped back and finished third, 27 seconds adrift.

The 184-kilometres route, much of it on dirt roads in the Crete Senesi hills and on the compacted white gravel that gives the event its name, was the same as last year.

It followed a course which started and finished in Siena.

"It's unbelievable," said Alaphilippe to Eurosport.

"I was focused all day on the finale. 

"I was lucky to never crash nor have a flat tyre. 

"My team did a great job in protecting me.

"Jakob Fuglsang was very strong, but I made no mistake. 

"However, I wasn't confident in winning until the last corner. 

"This is a wonderful victory."

The women's race began their WorldTour season and was won by Dutch rider Annemiek van Vleuten.

Riding for Mitchelton–Scott, the double world time trial champion captured her first race win since returning from a knee injury last year.

She broke away on the final gravel section and the overall WorldTour winner held on to win in 3:48.49.

Anika Langvad of Denmark and Boels-Dolmans was 37 seconds behind in second as third went to Kasia Niewiadoma of Poland and Canyon-SRAM, 40 seconds back. 

The men's WorldTour season will continue tomorrow with the start of the Paris-Nice stage race.

The 77th edition starts with a stage around the royal city of Saint-Germain-en-Laye.

Mountain stages will take centre stage at the end of the week, but sprinters will also have opportunities in the early going.

The race concludes on March 17.