Valverde placed seventh overall in the Vuelta a España on Sunday and cannot now be beaten in the WorldTour with just one event remaining: Il Lombardia on October 4.
As befits the title, Valverde has been the most consistent rider throughout the 2015 WorldTour season, notably winning Liege-Bastogne-Liege and La Fleche Wallonne, finishing third in the Tour de France and making numerous appearances in the top 10 of key races.
In addition to his two WorldTour titles, Valverde also topped the ranking for the WorldTour's predecessor, the ProTour, in 2006 and 2008.
Vuelta a España winner Fabio Aru (Astana) leaps up the WorldTour ranking from 14th to fifth, with Vuelta runner-up Joaquim Rodriguez (Katusha) occupying second place behind Valverde.
Top-placed British rider in Tour de France winner Chris Froome (Sky) in sixth place. Welshman Geraint Thomas (Sky) slips from 10th to 13th.
After his second place in the Grand Prix Cycliste de Montréal on Sunday, Briton Adam Yates (Orica-GreenEdge) has moved up from 43rd to 33rd spot, just one place in front of twin brother Simon.
Katusha remains at the top of the WorldTour ranking-by-team as Movistar move ahead of Team Sky into second place.
Spain is by far the strongest nation overall ahead of Colombia and Great Britain in third.
The WorldTour winners will, for the first time, be honoured at a special gala dinner, scheduled to be held in Abu Dhabi during this year's inaugural Abu Dhabi Tour (October 8-11).
Watch: Five most exciting road bikes of 2016
The next and final counting event in the 2015 UCI WorldTour is Il Lombardia (the Tour of Lombardy) in Italy on October 4.
WorldTour points are awarded for one-day race, tour stage and stage race overall finishing positions for counting events. The amount of points awarded depends on the ranking of the event. For example, winning the Tour de France overall gives a rider twice as many points as winning the Eneco Tour overall.
UCI WorldTour rankings (at September 13 after the Vuelta a Espana and GP Montréal)
1. Alejandro Valverde (Spa) Movistar 615 points
2. Joaquim Rodriguez (Spa) Katusha 474 points
3. Nairo Quintana (Col) Movistar 457 points
4. Alexander Kristoff (Nor) Katusha 453 points
5. Fabio Aru (Ita) Astana 448 points
6. Chris Froome (GBr) Team Sky 430 points
7. Alberto Contador (Spa) Tinkoff-Saxo 407 points
8. Greg Van Avermaet (Bel) BMC Racing 322 points
9. Rui Costa (Por) Lampre-Merida 324 points
10. Richie Porte (Aus) Team Sky 314 points
13. Geraint Thomas (GBr) Team Sky 283 points
33. Adam Yates (GBr) Orica-GreenEdge 150 points
34. Simon Yates (GBr) Orica-GreenEdge 148 points
105. Mark Cavendish (GBr) Etixx-QuickStep 30 points
120. Luke Rowe (GBr) Team Sky 20 points
166. Peter Kennaugh (GBr) Team Sky 6 points
1. Katusha 1526 points
2. Movistar 1419 points
3. Team Sky 1254 points
4. Etixx-QuickStep 988 points
5. Tinkoff-Saxo 929 points
1. Spain 1833 points
2. Colombia 1069 points
3. Great Britain 1041 points
4. Italy 1006 points
5. Belgium 905 points
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