BETHESDA, Md. — In Gee Chun is alone atop the Women’s PGA Championship leaderboard following a sensational start.

In fact, no player has ever been further ahead after 18 holes at a women’s major.

Chun breezed to an 8-under 64 on Thursday to hold a 5-stroke advantage after the first round at Congressional. While most of the field slogged through the day on the wet Blue Course, Chun birdied seven of eight holes during one stretch. She was 7 shots ahead when she finished her round and ended up tying a record for the largest 18-hole lead at a major.

Mickey Wright led this tournament by five after the first round in 1961.

“I don’t know what golf course In Gee is playing,” defending champion Nelly Korda said after finishing her round of 71.

Chun was playing the same course as everyone else, one that went through a full restoration last year. There was heavy rain in the area overnight and more precipitation during play Thursday morning. That softened the course but also made Congressional’s length — 6,809 yards for this first round — more of a factor.

No big deal for Chun, a two-time major winner.

“The course, after a lot of rain, feels longer,” the 27-year-old from South Korea said. “At the same time, greens were softer. So I think it was just a balance.”

Although there was plenty of golf left to play, Chun’s big lead certainly turned heads.

“I can’t stop staring at the leaderboard,” Justin Thomas tweeted. “Leading by 7 halfway thru day 1!!!!”

Pornanong Phatlum and Hye-Jin Choi shot bogey-free rounds of 69 to cut Chun’s lead to 5, but that was still a big enough advantage to tie Wright’s mark. The 1961 tournament was one of a record four victories by Wright at this event. Chun is trying for her first.

Chun set a major championship record — for men or women — when she won the Evian Championship in 2016 at 21 under. She also won the U.S. Women’s Open the previous year.

Paula Reto and Jennifer Chang were at 2 under. Korda and playing partner Brooke Henderson were part of a nine-player group at 1 under. One example of how challenging the course was: Korda hit driver, hybrid and 7-wood while making par on the 587-yard ninth hole.

“That’s the longest par 5 I’ve ever played,” she said. “I was happy to play the front nine even.”

Chun, who started on the back nine, birdied Nos. 15, 16, 17 and 18. After a bogey on No. 1, she rebounded with three more birdies in a row.

Chun hit all 14 fairways and said she passed the time by discussing non-golf topics with caddie Dean Herden.

“We talk about the kiwis because I love to eat kiwis on the course,” she said. “It’s really tough to find a good kiwi from the supermarket. Luckily, we have a good Korean supermarket near here, so I got a good gold kiwi from there.”

If Chun keeps playing like this, she might find it easy to relax on the course, but she’ll have a talented group of challengers chasing her. Jennifer Kupcho, who won her first major at the Chevron Championship earlier this year, was 1 under. Phatlum’s impressive round included an ace on the 199-yard second.

Inbee Park, Lydia Ko and world No. 1 Jin Young Ko all shot 72, 1 stoke better than U.S. Women’s Open champ Minjee Lee.

In fact, if not for Chun, a lot of players could feel pretty close to the lead.

“I feel like I played really well. The course is really hard,” Kupcho said. “I don’t really know how In Gee is 8 under right now. That’s definitely an outlier.”

NOTES

Emma Talley (78) finished while putting with a wedge after her putter was damaged during the round. … Lizette Salas and Cristie Kerr both shot 80.