South Korean Park Sung-hyun said "it hasn't hit me yet" after becoming the first LPGA Tour rookie to get to number one in the world rankings.
"I was very surprised and amazed by what I've achieved," Park told LPGA.com.
"This is an honour for my whole family."
Park has achieved nine top-10 finishes, top-20 finishes at three other majors and never missed a cut in her 29 career LPGA Tour starts.
She has taken over from compatriot Ryu So-yeon at the top of the rankings and is the fourth South Korean world number one since the rankings were introduced in 2006.