South Koreans Chun In-gee and Park Sung-hyun each carded bogey-free rounds of 63 to claim a share of the opening-day lead at the Evian Championship.
At eight under par, Chun and Park ended Thursday one clear of Shanshan Feng and Annie Park, with Angela Stanford fifth at six under.
World number one and defending champion Lydia Ko had to settle for a 70 on Thursday, leaving her seven shots off the pace, while British Open winner Ariya Jutanugarn, who played alongside Chun, started with a disappointing 73.
Chun made a wonderful start to the tournament and turned in 29 courtesy of six front-nine birdies.
Further gains at the 11th and 13th ensured she was comfortably the pick of the morning starters in France, but her score was matched later in the day.
Park Sung-hyun - tied for third at the US Women's Open earlier this year having led at halfway - picked up her eighth birdie at the 18th to earn a share of first, while Feng and Annie Park, who eagled the par-five 13th, closed to within one of the lead.
Reflecting on her performance, Chun told reporters: "Before the round I felt really nervous, and it was windy, and there was a thunderstorm this morning, so I tried to focus more on my game.
"I could see the putting lines very well, and I was so good rolling the ball on those lines."