The 19-year-old Kiwi’s dramatic one-shot success at Mission Hills in Rancho Mirage saw her become become the youngest two-time major winner, man or woman, since Young Tom Morris in 1869.
“It’s an amazing feeling,” she admitted after knocking her approach almost stiff to finish with a birdie-4 for a closing 69 and a 12-under-par total of 276, pipping England’s Charley Hull (69) and Korean In Ghee Chun (70).
Thailand’s Jutanugarn led by two shots with three to play only to finish bogey-bogey-bogey as she ended up fourth on ten-under.
Ko has now won back-to-back majors after making the breakthrough in last year’s Evian Championship in France.
This was also her second victory in a row after warming up for the event with a win in the Kia Classic in Carlsbad a week earlier.
She’s now chalked up 12 LPGA Tour triumphs, a remarkable haul for someone who doesn’t turn 19 until late next month.
“It’s been a long week and I was able to match some clutch putts,” said a delighted Ko before making the traditional champion’s leap into Poppie’s Pond.
Asked if she’d dreamt of winning majors starting out on her career, Ko admitted with a smile: “Not really.
“I just wanted to enjoy playing on the LPGA Tour as that was always my dream. For these amazing things to be happening to me is unbelievable.”
This was 20-year-old Hull’s best performance in a major, improving on a seventh place in the same event two years ago.
Catriona Matthew’s hopes of making a last-round charge were unhinged by a triple-bogey 8 at the second, where she went out of bounds.
The North Berwick woman repaired some of the damage with a last-hole eagle but finised joint-32nd after a closing 75.