Student Amy Yang sank a 23-foot putt to take the ANZ Masters title and become the first amateur to win on the European Tour for more than 20 years.
ANZ MASTERS LEADERBOARD
US unless stated
-13 A Yang (Kor) (won play-off)
-13 C Cartwright
-12 T Ya-ni (Tai), T Joh, L Stahle (Swe)
-8 K Taylor (Eng)
-4 M McKay (Sco), R Coakley (Ire)
-3 K Webb (Aus), L Davies (Eng)
+1 A Miyazato (Jap)
The Korean, 16, bogied the last to tie with Catherine Cartwright but won with a birdie at the first extra hole.
As the leading professional, American Cartwright, who shot 68, took home the winner's cheque of $90,000 (£51,000).
Two other amateurs, Taiwan's Tseng Ya-ni and Tiffany Joh of the US tied for third with Sweden's Louise Stahle.
Yang, who had led since the second round, burst into tears after sinking her monster winning putt and hugged her father James, who was caddying for her.
She shot a two-under-par 70 for a final total of 275 on the Royal Pines course - matching the 13-under mark set earlier by Cartwright.
Yang's victory was the first by an amateur in a major tournament in Australia and the first on the European tour since Scotland's Gillian Stewart won at the Belfry in England in 1984.
Yang's coach, Laurie Montague, who runs a nearby golf academy, said her victory could lead to invitations to play in international tournaments.
"She could get some offers, but it would be up to Amy and her parents to explore those opportunities," he said.
"I've never met anyone so humble. Her game is just so solid, she doesn't get too excited. When it comes to maturity on the golf course, she was way beyond her years."
Asked if she was surprised to be beaten by such a young opponent, Cartwright, 22, replied: "I don't think it matters whether you're 16 or 60 if you have the talent.
"I didn't even know she was an amateur until my caddie told me.
"I learned a lot about my myself out there today and it will help my confidence."
Ya-ni shot an eight-under-par 64 to rocket up the field, while Joh finished with a 69 and Stahle fired a 68.
Defending champion Karrie Webb - aiming for her sixth Masters title - had a disappointing tournament, finishing tied for 33rd with England's Laura Davies.
Davies, who has won the Masters three times, ended with a 69 while Webb had a 72.
Kirsty Taylor led the British challenge, finishing with a 69 for an eight-under total of 280.
Japan's Ai Miyazato, who led for three rounds last year before losing to Webb on the final day, was on one-over after a 72.