Paris - Romanian Simona Halep's run to the final of the China Open, which she lost to France's Caroline Garcia, saw her take over at the top of the latest WTA Tour rankings released on Monday.
The 26-year-old Halep becomes the first Romanian woman to be ranked world No 1.
She succeeds Spain's Garbine Muguruza, who is now in second.
WTA standings as of October 9:
1. Simona Halep (ROM) 6,175
2. Garbine Muguruza (ESP) 6,135
3. Karolina Pliskova (CZE) 5,605
4. Elina Svitolina (UKR) 5,465
5. Venus Williams (USA) 4,652
6. Caroline Wozniacki (DEN) 4,640
7. Jelena Ostapenko (LAT) 4,510
8. Svetlana Kuznetsova (RUS) 4,005
9. Caroline Garcia (FRA) 3,860
10. Johanna Konta (GBR) 3,795
11. Dominika Cibulkova (SVK) 3,330
12. Angelique Kerber (GER) 3,181
13. Kristina Mladenovic (FRA) 3,035
14. Madison Keys (USA) 2,823
15. CoCo Vandeweghe (USA) 2,819
16. Sloane Stephens (USA) 2,722
17. Petra Kvitova (CZE) 2,532
18. Agnieszka Radwanska (POL) 2,370
19. Elena Vesnina (RUS) 2,300
20. Anastasija Sevastova (LAT) 2,295