Marianne Vos further cemented her status as one of the greatest cyclists of all time by soloing to her second successive world road race title as Britain's Lizzie Armitstead finished in 19th place.
Vos, the Olympic and defending world champion, surged away from a select lead group of riders on the day's final climb and then powered on to a dominant 15-second victory.
Armitstead rode almost all of the race without help after her three Great Britain team-mates were dropped early on and while she fared well on her own, she couldn't follow a significant attack just under 30km from home and fell away, eventually finishing 5min 28sec down.
Vos, 26, was one of seven riders who successfully infiltrated the move and the group later swelled to 13 as they made their way on to the last of five laps of a 16.6km finishing circuit around Florence.
Each lap contained two climbs - the 4.3km Fiesole and the steep, 600m Via Salviati - and both proved pivotal in the finale.
Evelyn Stevens (United States) and then Anna van der Breggen (Netherlands) attacked on the Fiesole to thin the group down to just five, and then Vos launched her decisive move on the steepest section of the Via Salviati, which reaches a maximum gradient of 16 per cent.
Only Sweden's Emma Johansson and Italy's Rossella Ratto could give chase, but they soon found themselves 150m adrift of the all-conquering Dutch rider on the descent to the finish line and the gap never looked like being closed.
Vos too strong
Vos, who has now won the world road race title three times, time-trialled her way to the finish line and was celebrating by as early as 100m to go.
Johansson sprinted to the silver medal, with Ratto, who is only 19, collecting the bronze.
Only 46 riders finished the race, with Britain's Lucy Garner, Nikki Harris and Katie Colclough among those who pulled out after falling off the pace.
Colclough, 23, was racing for the final time before retiring from professional cycling.
Women's road race result
1 Marianne Vos (Ned), 3:44:00
2 Emma Johansson (Swe), +15sec
3 Rossella Ratto (Ita), same time
4 Anna van der Breggen (Ned), +33
5 Evelyn Stevens (USA), +46
6 Linda Villumsen (NZ), +50
7 Tatiana Guderzo (Ita), +52
8 Elisa Longho Borghini (Ita), st
9 Tiffany Cromwell (Aus), +1:40
10 Tatiana Antoshina (Rus), st
19 Lizzie Armitstead (GB), +5:28