CHICAGO – Australia's Jason Day won the BMW Championship on Sunday to seize golf's number one world ranking from Rory McIlroy.

The 27-year-old PGA Champion notched his fifth win of the season to become just the third Australian to reach golf's summit after Greg Norman and Adam Scott. Ranked third in the world coming in, Day moved past both world number two Jordan Spieth and McIlroy.

He fired a two-under par 69 in the final round for a 22-under total of 262 and a six-shot triumph over American Daniel Berger.