Inbee Park and Pernilla Lindberg played until it was too dark to see Sunday night and still couldn't decide the ANA Inspiration.
They'll return to Mission Hills on Monday morning for the fifth extra hole in the LPGA Tour's first major of the season.
"Inbee's one of the best female golfers of all time," Lindberg said.
"So to even have a chance to go out and beat her in a playoff, I think I'm going to sleep great tonight, and I'm going to be ready to go in the morning."
Jennifer Song, who was tied with Park and Lindberg at 15 under after 72 holes, dropped out with a par on the third extra hole.
Park and Lindberg then decided to take one more trip down the par-5 18th in fading light.
"They asked us quickly after the third play-off hole if we wanted to do one more, and both Inbee and I looked at each other quickly and said, 'Yes'," Lindberg said.
With portable lights and the scoreboard helping illuminate the green, Park holed a six-foo putt for par and Lindberg made a short putt to match.
They finished 15 minutes after sunset.
"I was a little nervous because No. 18 is not my favourite hole," Park said.
Play will resume at 8am on the par-4 10th in the first Monday finish in tournament history.
"Finally, we're playing a different hole tomorrow, so I'm excited about that," Park said.
Park, a 29-year-old South Korean former world No.1, won in 2013 at Mission Hills and is a seven-time major champion.
Swede Lindberg, the third-round leader, is trying to win her first professional title at age 31.
"I just kept grinding all day," Lindberg said.
"I've always said that the putting has been the strength of my game."
Australia's contingent was headed by rookie Hannah Green, who carded a sizzling 66 on Sunday to finish in a tie for 16th.
Minjee Lee had a 73 to slip to tied 25th while Sarah Jane Smith (69) was tied 40th.
Jessica Korda (66) and Ariya Jutanugarn (65) were tied for fourth at 14 under while Michelle Wie had a 69 to tie for 30th at five under, again fighting though dizziness, which has hampered her week, caused by a virus.
