South Korea's Chun In-gee fired a record-equalling eight-under-par 64 to surge into a commanding early at the Women's PGA Championship on Thursday.
The 27-year-old two-time major champion reeled off nine birdies and only one bogey at Congressional Country Club outside Washington to match the lowest opening round in the history of the Women's PGA Championship set by Nicole Castrale in 2006.
Chun's remarkable round was also a course record at Congressional, the historic 98-year-old venue which is hosting a women's major championship for the first time.
Shrugging off wet conditions that made the course play longer -- two inches of rain had been dumped on the layout overnight -- Chun's round erupted just before the turn when she reeled off four straight birdies to move to five under.
A bogey on her 10th hole of the day briefly interrupted her momentum before another trio of birdies on her 11th, 12th and 13th holes took her to seven under.
One more birdie three holes from home left her on eight under.
"I didn't think about all the history from the course today," Chun said. "I just keep going to make birdie as much as I can.
"After a lot of rain -- course feels longer. I had a couple of good shots with my woods. That's how I had birdie chance.
"At the same time the greens were softer, so I think it was just good balance."
Chun's spectacular round left her in the clubhouse five shots clear of her nearest finisher, compatriot Choi Hye-jin, who posted a three-under-par 69, with the afternoon flight still on the course.
South Africa's Paula Reto was in the clubhouse on two under, while eight other players including in-form Jennifer Kupcho, Canada's Brooke Henderson and defending champion Nelly Korda fired one-under-par 71s.
Korda battled through the conditions with three birdies and two bogeys -- including a five on the 18th -- but was satisfied to duck under par.
However the American admitted she was taken aback by Chun's blazing opening round.
"Any first round under par is good at a major," Korda said. "I don't know what golf course In-gee is playing. She must be playing really well.
"I would think when I teed it up today, I would be very happy with the score that I shot."
Korda was in no doubt about how rain-soaked course had played.
"Long. It was definitely really, really long," she said. "Especially for me. I am one of the longer hitters on the tour, and it was long."