Paris - The ATP Tour officially crowned Andy Murray as world No 1 on Monday as Roger Federer fell out of the top 10 for the first time in 14 years.
Novak Djokovic's quarter-final defeat to Marin Cilic in the Paris Masters saw the Serb dethroned after 122 weeks as number one.
Murray, who won in Paris for his fourth straight tournament win, is the oldest player at 29 to become number one for the first time.
Swiss legend Federer, who has not played since ending his season in July with a knee injury, dropped seven places to 15th.
Federer, who spent 302 weeks as world number one, had been in the world top 10 since October 13, 2002.
Top 20 in the latest ATP rankings:
1. Andy Murray (GBR) 11 185
2. Novak Djokovic (SRB) 10 780
3. Stan Wawrinka (SUI) 5 115
4. Milos Raonic (CAN) 5 050
5. Kei Nishikori (JPN) 4 705
6. Gal Monfils (FRA) 3 625
7. Marin Cilic (CRO) 3 450
8. Rafael Nadal (ESP) 3 300
9. Dominic Thiem (AUT) 3 215
10. Tomas Berdych (CZE) 3 060
11. David Goffin (BEL) 2 780
12. Jo-Wilfried Tsonga (FRA) 2 550
13. Nick Kyrgios (AUS) 2 460
14. Roberto Bautista (ESP) 2 350
15. Lucas Pouille (FRA) 2 196
16. Roger Federer (SUI) 2 130
17. Grigor Dimitrov (BUL) 2 035
18. Richard Gasquet (FRA) 1 885
19. John Isner (USA) 1 850
20. Ivo Karlovic (CRO) 1 795