Jason Day has won the BMW Championship to become world golf’s new number one.
The Beaudesert local had already put in all the hard work in the opening three rounds but continued his stunning performance into the fourth and final round in Chicago on Monday.
Day finished on 22-under-par, six shots ahead of second-placed American Daniel Berger.
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He is the third, but youngest, Australian behind Greg Norman and Adam Scott to assume the top spot.
Since missing a playoff by one shot at the British Open in July, Day has won the Canadian Open, his first major at the PGA Championship and the opening playoff event at the Barclays.
This is now his fifth win in 2015 and seventh US PGA tour win overall.
He wqs already guaranteed passage through to the final FedEx Cup playoff event next week where, should he win at East Lake Golf Club, he will also claim the $US10 million ($A13.94 million) bonus.