He replaces Rory McIlroy at the top of the standings.
Spain's Jon Rahm is golf's new world number one.
The 25-year-old won the Memorial tournament in Ohio last night, with a final round of 75 enough for him to win by three on nine under par.
Rahm is the second Spaniard, after Seve Ballesteros, to top the rankings.
He replaces Rory McIlroy, who finished back on four over, after a 78 yesterday.
Rahm says he's dedicating the win to relatives lost during the coronavirus pandemic: