Mathieu van der Poel completed a Netherlands double in Strade Bianche after Chantal van den Broek-Blaak had earlier won the women’s race in Siena.
Van der Poel, 26, punched clear on the final climb to win by five seconds from world champion Julian Alaphilippe.
Ex-Tour de France winner Egan Bernal was third with Ineos Grenadiers team-mate, Britain’s Thomas Pidcock, fifth.
Van den Broek-Blaak, 31, won by seven seconds from Elisa Longo Borghini.
In the men’s race Pidcock, 21, was the first British rider home, 54 seconds behind the winner, with Simon Carr 11th and Owain Doull 30th.
After securing victory on the famous white dirt roads of Tuscany, Van der Poel said: “Strade is one of the races I really wanted to win, and it’s really cool to win it today.
“I felt pretty good, I launched an attack on the last gravel section and I came with Bernal and Alaphilippe in the lead.
“We did a pretty strong ride the three of us. I felt I had something left in the legs to go all out on the last climb, and it’s amazing to finish it off in this way.”
Van den Broek-Blaak is the fourth successive Dutch winner of the women’s event, following Anna van der Breggen (2018) and Annemiek van Vleuten in 2019 and 2020.