Singh's victory in the Deutche Bank Championship -- his sixth title of the year -- moved him to the top of the rankings.
Woods, who finished in a tie for second in the Deutsche Bank event, had been No. 1 for 264 straight weeks.
In the latest ratings, released by the computerized Official World Golf Ranking, which is endorsed by the world's major golf tours, Els remained at No. 3, followed by Phil Mickelson and David Love III.
Sergio Garcia is No. 11, Stewart Cink No. 12 and Stewart Appleby No. 13. Rounding out the top 20 are Kenny Perry, Chad Campbell, Darren Clarke, Chris DiMarco, Todd Hamilton, Stephen Ames and Scott Verplank.