Ayako Uehara fired a 7-under-par 65 to grab the first-round lead at the AmazingCre Portland Classic on Thursday in Portland, Ore.
Uehara rolled in eight birdies and recorded just one bogey at Columbia Edgewater Country Club to take a one-shot lead over Australia's Hannah Green, who shot a 6-under 66.
World No 2 Nelly Korda opened with a 5-under 67 to join a tie for third with Caroline Inglis and Japan's Ayaka Furue and Hinako Shibuno.
Uehara both started and finished her round strongly. She made five birdies on the front nine and three more over her final four holes, including Nos. 17 and 18.
The 38-year-old has won three times in Japan but is seeking her first LPGA Tour victory. She said being out front won't affect how she approaches the second round.
"I don't think so," Uehara said. "I will do just my game and then focus one at a time."
Green, a major winner and the 2019 Portland champion, sandwiched eight birdies between her two bogeys at the third and 18th holes. She birdied three of the four par-5 holes on the course and both par-3s on the back nine.
"Unfortunately made a bogey on the last, but don't want to dwell on that," Green said. "I guess I didn't hit a great shot, but I also got unlucky where I finished up.
"Only missed two greens today, so I can't be too down on myself. Yeah, just keep giving myself opportunities, and, yeah, hopefully continue to hole those putts."
Ranked No 17 in the world, Green is looking for her first victory since the 2019 win in Portland. Green finished second in April at the DIO Implant LA Open and shot a 9-under 62 in the second round of the Dana Open earlier this month before finishing 10th.
After missing four months of the season with a blood clot, Korda is searching for her first victory of the year. She tied for second twice, including in her last start, the CP Women's Open.
Korda had a colorful card, following a double-bogey 6 at the sixth hole with an eagle 3 at the seventh. She also made seven birdies and two bogeys.
"Mainly my missed drives," Korda said of her difficulties on the day. "It's so tree-lined here. It's such a beautiful golf course. So many big, tall trees. But they're very thick and they're very high. ... So when you miss a fairway it's hard to get through the trees."
Evian Championship winner Brooke Henderson of Canada opened with a 4-under 68. She was tied for seventh with countrywoman Alena Sharp, Lilia Vu, Anne van Dam of the Netherlands, Jenny Shin of South Korea and Tiffany Chan of Hong Kong.
Defending champion Jin Young Ko of South Korea, the No 1 player in the world, withdrew from the event earlier this week to rest a wrist injury.
First Round Leading Scores (USA unless noted, 72):
65 - Ayako Uehara (JPN)
66 - Hannah Green (AUS)
67 - Ayaka Furue (JPN), Nelly Korda, Hinako Shibuno (JPN), Caroline Inglis
68 - Tiffany Chan (HKG), Brooke Henderson (CAN), Anne van Dam (NED), Alena Sharp (CAN), Jenny Shin (KOR), Lilia Vu
69 - Rachel Rohanna, Carlota Ciganda (ESP), Mina Harigae, Maja Stark (SWE), Choi Na-yeon (KOR), Angel Yin, Jenny Coleman, Daniela Darquea (ECU), Zhang Weiwei (CHN), Sarah Kemp (AUS), Aditi Ashok (IND), Ana Belac (SLV), Lauren Hartlage