Matthew Wolff, a 21-year-old American making only his second major start, fired a five-under par 65 to seize a two-stroke lead after Saturday's third round of the US Open.
The 2019 US college champion for Oklahoma State, who shared fourth at last month's PGA Championship, solved wicked Winged Foot to stand on five-under 205 after 54 holes.
Wolff found only two of 14 fairways but blasted from the deep grass onto 12 greens in regulation and made six birdies against a lone bogey.
"Every time I was in the rough and had a good lie I took advantage of it," Wolff said. "I minimised the mistakes. It was a good day all around.
"I got really fortunate with the lies in the rough. I just stuck with my game. It was a grind out there."
American Bryson DeChambeau was second on 207 after shooting 70. He opened with back-to-back bogeys and closed with a bogey after birdies at 16 and 17.
"I felt like I was trying to hope it into the fairway all day. That's not what you want at a US Open," said DeChambeau. "I was able to show resilience, coming back to shoot par after two bogeys."
South Africa's Louis Oosthuizen, the 2010 British Open champion, fired a 68 to stand third on 209.
"Any under-par round at a US Open you'll take," Oosthuizen said. "(Wind) definitely died down for us. Definitely lucky on the draw today."
World No 36 Wolff, who won his first PGA Tour title at Minneapolis in only his third tour start, needed only 10 putts over his first nine holes, shooting an astonishing 30 on the front nine on the famed Mamaroneck, New York, layout.
Through three rounds, he has hit only 12 fairways, the fewest of any US Open leader since 1983.
"I tried to shoot as low as possible with hitting as few fairways as possible," Wolff joked. "That will get me ready for tomorrow.
"I'm just going to go out there, do the same thing and whatever happens happens."
Wolff matched Winged Foot's lowest US Open round ever, Justin Thomas's opening 65, after starting the day four adrift of leader Patrick Reed, who stumbled to a 77 with eight bogeys and a double bogey to stand on 213 after leading Wolff by three early.
Wolff made a 14-foot birdie putt at the opening hole, a 15-footer to birdie the par-4 fourth, a five-footer for birdie at six and a 13-foot birdie putt at the par-3 seventh.
He closed the front nine with a three-foot birdie putt at the par-5 ninth then grinded out six pars in a row before his first bogey at the 16th, missing an eight-footer for par.
At 18, Wolff bounced off the top off deep rough into a shorter cut, blasted to 10 feet from the cup and sank his birdie putt.
"I feel really good with my putting," Wolff said. "I just told myself it was just another putt."
Oosthuizen had four birdies and two bogeys, each answered by a birdie on the following hole. The South African said he needs a repeat performance to capture his first major in a decade.
"I need to play pretty similar to what I did today," he said. "A lot can happen even in the last two, three holes, so try and get yourself in a position with three, four, five holes to go and see what you can do.
"Just need to go out and play some good golf tomorrow."
Japan's Hideki Matsuyama, who made four birdies and three bogeys in his first seven holes, scrambled to a 70 to share fourth alongside Americans Xander Schauffele and Harris English on level par 210.
Matsuyama, chasing his first major crown, opened with a birdie, followed with back-to-back bogeys, then reeled off three birdies in a row before a three-putt bogey at the par-3 seventh. A double bogey at 17 after finding deep rough and a bunker dropped him from the sub-par pack.
"Hopefully tomorrow I can make the same number of birdies without the bogeys," Matsuyama said. "I hit some good putts today, but at the same time I hit some bad ones. Tomorrow I just pray that I have more makes."
Four-time major winner Rory McIlroy was seventh on 211 after a 68, six back but liking his chances of a first major win since the 2014 PGA.
"I've got a good chance," McIlroy said. "(Six) is not a lot on this golf course. I feel like I'm right in it."
Third-round scores on Saturday from the 120th US Open Golf Championship at Winged Foot in Mamaroneck, New York (USA unless noted):
205 - Matthew Wolff 66-74-65
207 - Bryson DeChambeau 69-68-70
209 - Louis Oosthuizen (RSA) 67-74-68
210 - Hideki Matsuyama (JPN) 71-69-70, Xander Schauffele 68-72-70, Harris English 68-70-72
211 - Rory McIlroy (NIR) 67-76-68
212 - Zach Johnson 70-74-68, Viktor Hovland (NOR) 71-71-70, Rafa Cabrera Bello (ESP) 68-70-74
213 - Alex Noren (SWE) 72-74-67, Lucas Glover 71-71-71, Webb Simpson 71-71-71, Joaquin Niemann (CHI) 68-73-72, Thomas Pieters (BEL) 66-74-73, Patrick Reed 66-70-77
214 - Adam Long 71-74-69, Will Zalatoris 70-74-70, Billy Horschel 72-70-72, Justin Thomas 65-73-76
215 - Paul Casey (ENG) 76-70-69, Dustin Johnson 73-70-72, Lee Westwood (ENG) 67-76-72, Tony Finau 69-73-73, Bubba Watson 72-69-74, Brendon Todd 68-72-75
216 - Lanto Griffin 71-74-71, Thomas Detry (GER) 71-72-73, Renato Paratore (ITA) 71-72-73, Jason Kokrak 68-71-77
217 - Charles Howell 73-72-72, Daniel Berger 73-70-74, Jon Rahm (ESP) 69-72-76
218 - Christiaan Bezuidenhout (RSA) 70-76-72, Rickie Fowler 69-77-72, Matt Wallace (ENG) 70-75-73, Im Sung-jae (KOR) 70-75-73
219 - Adam Scott 71-74-74, Adam Hadwin (CAN) 72-73-74
220 - Ryo Ishikawa (JPN) 72-74-74, Lucas Herbert (AUS) 72-74-74, Romain Langasque (FRA) 71-74-75, Michael Thompson 70-75-75, Taylor Pendrith (CAN) 71-74-75, Erik van Rooyen (RSA) 70-74-76, Stephan Jaeger (GER) 71-70-79
221 - Brian Harman 74-72-75, Bernd Wiesberger (AUT) 73-72-76, Tyler Duncan 73-71-77
222 - Robert MacIntyre (SCO) 74-72-76, Patrick Cantlay 70-76-76, Jason Day (AUS) 72-74-76, Sebastian Munoz (COL) 71-74-77, Cameron Smith (AUS) 71-73-78
223 - Shane Lowry (IRL) 76-70-77, Chesson Hadley 73-73-77, Danny Lee (NZL) 70-75-78, Shugo Imahira (JPN) 71-74-78, Rory Sabbatini (SVK) 69-76-78
224 - Troy Merritt 72-74-78, John Pak 69-76-79
225 - Abraham Ancer (MEX) 71-75-79