England's Charley Hull completed a fine recovery from her opening 74, claiming a top-10 finish with a four-birdie 69 with her bogey at the 15th being her only dropped shot over the final three rounds.
Ko, who started Sunday with a four-shot break, has picked up one birdie on her front nine at Kooyonga to be 12-under for the tournament.
Ko is the first LPGA player in 67 years to win in her official debut. The next two tour stops will be the Honda LPGA Thailand this week, where Lexi Thompson, a Player of the Year threat, will make her second start of 2018, followed by the HSBC Women's World Championship in Singapore before the LPGA returns to the U.S.at the Bank of Hope Founders Cup in Phoenix.
But the victory in her debut stage is more impressive, as it's a badge of honor even Pak Se-ri and Park Sung-hyun haven't earned.
"I didn't think it was on line and went to pick up the tee".
Ko Jin-young poses with her trophy after winning the Women's Australian Open in Adelaide on Sunday. "Scary Dean", she calls him, and she added today that Herden's face had been grim throughout. With his help, she dominated the field from the first round, taking sole lead at seven under par.
Ko said she felt "lots" of nerves over the final round.
This allowed Choi to get one shot behind Ko after the first nine.
She birdied four of her initial 10 holes to be among a group of 10 golfers on four under 68.
By making a birdie putt on the par-4 13th, about six meters (19.7 feet) long, Ko extended her lead by three.
Both Ko and Choi found success on the Korean LPGA Tour before competing in LPGA events.
Not many people had heard of Ko in Australia prior to her arrival at Kooyonga Golf Club - but they certainly have now, after she enjoyed a dominant wire-to-wire victory. In the past three seasons, the award winners have all been Korean.
Na finished the tournament at three-under while Australia's top-ranked golfer, world No.17 Minjee Lee, ended at eight-under in a tie for fifth with American Marina Alex. Shin, who won the tournament in 2013, lost her chance to defend the title with a double bogey on par-4 eighth.