South Africa's Branden Grace carded the first 62 in men's major championship history as Jordan Spieth took a step closer to his own place in the record books at Royal Birkdale.
Grace took advantage of ideal conditions and a par-70 layout reduced to 7,027 yards to card eight birdies and surge through the field in the 146th Open Championship.
The 29-year-old's brilliant effort took him from four over par to four under, although that was still seven shots behind two-time major winner Spieth, who carded a second bogey-free 65 of the week.
At 11 under par, Spieth enjoyed a three-shot lead over playing partner Matt Kuchar, with 20-year-old Canadian debutant Austin Connelly - a good friend of Spieth - three shots further back alongside US Open champion Brooks Koepka.
Grace shared fifth place with world number two Hideki Matsuyama, with defending champion Henrik Stenson, world number one Dustin Johnson, Rafael Cabrera Bello and Chan Kim on three under.
Rory McIlroy squandered a flying start to card a 69 and finish on two under alongside Scotland's Richie Ramsay and the English duo of Ross Fisher and Ian Poulter.
A victory on Sunday would make Spieth only the second player after Jack Nicklaus to have won three of the game's four majors before the age of 24.
"That would be incredible," Spieth said. "I've had a five-shot lead in a major and squandered it before. I've had the high and the humbling so I will keep my head down and not get ahead of myself."
But if he does get his hands on the Claret Jug, the 23-year-old could then surpass the record of Tiger Woods as the youngest player to complete a career grand slam in the US PGA Championship at Quail Hollow in August.
The bad news for the chasing pack is that Spieth has converted five of his last 36-hole leads into victories. The good news could be that the exception is last year's Masters, where he blew that five-shot lead with just nine holes to play.
Spieth had taken a two-shot advantage into the third round, and despite three birdies in the first eight holes, was initially unable to shake off the attentions of Ryder Cup team-mate Kuchar.
Kuchar matched Spieth's front nine of 31 and briefly held a share of the lead when he birdied the 14th and 15th, but Spieth followed Kuchar in on the par-five 15th and saw Kuchar double bogey the next.
A birdie on the 17th saw Kuchar close the gap and he looked set to make another on the last, only to miss from six feet after Spieth had holed from more than twice the distance.
More than four hours earlier, Grace had tapped in for par on the same hole blissfully unaware of what he had just achieved.
" I didn't know what was going on on 18. I promise you," Grace said, who only realised when told by his caddie. " I was just so in the zone of playing, hole after hole.
"I knew I was obviously playing really well and making the turn in five under was pretty special. I thought if I could make a couple more on the back nine, then it's going to be a great score. I had no idea that 62 was obviously the lowest ever.
"N ow it makes the day even sweeter."
Remarkably, Grace's 62 looked like being matched soon after as Johnson played his first 10 holes in five under par, but the big-hitting American could only find one more birdie and settled for a 64.
The low scoring continued as McIlroy holed from four feet on the first, chipped in for birdie on the fourth and two-putted the short fifth for another after driving the green, only to bogey the seventh and eighth.
A birdie on the ninth revived hopes of a title challenge, but the 2014 champion barely escaped a fairway bunker on the 10th on his way to a double-bogey six.
"I was hitting it well, couldn't have asked to get off to a better start," McIlroy said. "I was really rolling and the bogeys on seven and eight stopped me in my tracks. I bounced back well on the ninth but the six on the 10th was a real kick in the teeth.
" I should have hit a club to take all the bunkers out of play but hit a three iron which was the worst club. It was a huge mental error and I lost the head a little bit there and didn't capitalise on some of the chances I gave myself coming in."
Stenson had all-but written off his chances of making a successful title defence after finishing 26th in last week's Scottish Open.
But the 41-year-old Swede, whose rental house was burgled during his first round on Thursday, joined Johnson on three under par after carding six birdies and a solitary bogey in a 65.