American Peter Uihlein shot a 12-under-par 60 at Kingsbarns as England's Tom Lewis took a one-shot lead at the Dunhill Links Championship.
Uihlein narrowly missed a 20-foot eagle putt at the last which would have made him the first man in European Tour history to break 60.
Lewis shot a 65 at St Andrews to lead by a shot from Dutchman Joost Luiten, who had a 63, also at Kingsbarns.
Uihlein's incredible round launched him up the leaderboard after a very ordinary 71 at Carnoustie on Thursday and he is now in a share for third place alongside five other players, two shots off the pace.
Last year, South African Branden Grace also shot 60 on the same course - one of three used for the pro-am event - and went on to lift the title, his fourth of the season.
Uihlein, who won his maiden title in Madeira in May, started on the back nine at Kingsbarns and followed a birdie on the 11th with an eagle on the 12th, before picking up birdies at the 17th and 18th to reach the turn in 31.
At that stage a 59 did not look on the cards, but the 24-year-old birdied the second, carded his second eagle of the day on the third and then birdied three of his next four holes.
A birdie chance went begging from 20 feet on the eighth to leave the former world No 1 amateur needing to eagle the ninth to create history, but his long-range effort slid just past the hole.
"I knew I needed to make an eagle and I thought I hit a good putt," said Uihlein, who recorded the 17th round of 60 on the European Tour"I thought it would come back to the right but it kept going left.
"Today started off with me hitting it close and not making anything and then I started holing it from everywhere. It was just one of those days that went for me.
"When I made that birdie on the 17th to go 11 under that was the first time 59 crossed my mind. I was in the zone out there and it was cool. I am definitely not as calm underneath (as it looked) but I just tried to stay with my routines and keep the same swing thought.
"I put a lot of work in during the off-season and even on my off weeks I'm still practising and grinding so it's nice to see the results so quickly."
Lewis added a 65 at St Andrews to his opening 64 at Kingsbarns to get to 15 under.
"Seven under is a good score at St Andrews but there was no wind today so I think you would be disappointed if you did not shoot better than five under," said Lewis, who won the Portugal Masters in his third event as a professional in 2011 but is down at 155 on the Race to Dubai and is battling to keep his card for next season.
"I feel like I am home again. Links golf suits me, I won the St Andrews Links Trophy here in 2011 and it's great to come back. I knew I had good form coming in but Friday has been my enemy this year so it's good to get it out of the way."
Luiten has won twice already this season in the Lyoness Open in Austria and the KLM Open on home soil in Zandvoort.