Who was the youngest number one ever in the Official World Golf Rankings for women?

Lydia Ko reached the number 1 ranking in women's golf on February 2, 2015. She was 17 yrs, 9 months and 9 days old.

More about the youngest number one in the Official World Golf Rankings for women

Lydia Ko won her first LPGA Tour event at just 15 years old and a few short years later she won her first major at just 18 years and 4 months of age.

Who was the youngest number one ever in the Official World Rankings for men?