Bruce Crampton set the PGA Championship 18-hole record with a 7-under 63 in the second round of the 1975 PGA Championship. Since then, 13 players have tied Crampton's mark for the best round at golf's fourth and final major of the season. The most recent are Brooks Koepka and Charl Schwartzel in the second round of the 2018 PGA Championship at Bellerive.
There have been 24 times a player has shot as 64 at the PGA Championship, including Francesco Molinari and Hideki Matsuyama in the second round at the 2017 PGA Championship.
Here are the 13 best rounds in PGA Championship history.
Charl Schwartzel, Brooks Koepka (2018)
Schwartzel (left) and Koepka scorched Bellerive in the second round of the 2018 PGA Championship to record matching 7-under 63s. Koepka made seven birdies in his round. Schwartzel made eight and had the lone bogey in the pairing.
Bruce Crampton (1975)
Twenty-four players have shot a 64 at the PGA Championship but Crampton was the first golfer to break through and card a 63. His performance at Firestone Country Club was a roller coaster as he shot 71-63-75-69 to finish second, two strokes behind Jack Nicklaus.
He was one of three players to finish under par.
Raymond Floyd (1982)
It took seven years for someone to match Crampton's historic performance and Floyd did so as part of a wire-to-wire win at Southern Hills. After shooting a 7-under 63 in the first round to take a three-stroke lead into Friday, he was the only player to start the PGA Championship with three sub-par rounds.
Despite shooting a 2-over 72 on Sunday, Floyd still won the 1982 PGA Championship by three strokes over Lanny Wadkins. It was the second time he won the PGA Championship and the third of the four majors he won in his career.
The nine-time major winner was forced to play catch-up after shooting a 2-over 74 in the first round of the 1984 PGA Championship at Shoal Creek. He was actually tied for the lead after shooting a 9-under 63 in the second round but he finished the weekend 69-71 compared to Lee Trevino's 67-69, as Trevino won by four strokes.
Player tied for second.
Vijay Singh (1993)
After a nine-year drought without a player shooting a 63 at the PGA Championship, Vijay Singh added his name to the record books in the second round of the 1993 PGA Championship at Inverness. The second round has been the most common round for 63s at the PGA Championship, where seven of the 13 record-low rounds have come on Friday.
Singh shot a 2-over 73 in the third round and finished in fourth, two strokes behind winner Paul Azinger.
There were two record-tying rounds at the 1995 PGA Championship at Riviera Country Club. Michael Bradley opened the week with an 8-under 63 in the first round to take a one-stroke lead entering Friday but he quickly faded.
Bradley finished the tournament tied for 54th at 1-under after shooting 73-73-74 to close the PGA Championship.
Brad Faxon (1995)
Three days after Bradley sprinted out of the gates, Faxon became the only player to ever shoot a 63 in the final round at the PGA Championship. Entering Sunday at 5-under for the tournament, Faxon made a strong push to close the 1995 PGA Championship to jump to fifth place at 13-under.
His 28 on the front nine stands as the best nine-hole score ever at the PGA Championship.
Jose Maria Olazabal (2000)
After shooting a 4-over 76 in the first round and being in danger of not making the cut, Olazabal became the first player to shoot a 63 in the third round. He tied for fourth, six strokes behind winner Tiger Woods, which was the best finish at the PGA Championship for the two-time Masters winner.
Mark O'Meara (2001)
Mark O'Meara went 32-31 – the most common front/back nine scores for players who have shot a 63 at the PGA Championship – in the second round at the 2001 PGA Championship. Despite his record-tying round before the weekend, he finished 13 strokes behind winner David Toms as O'Meara tied for 22nd at 2-under.
His second-round 63 was his only round under par at the tournament.
Thomas Bjorn (2005)
Bjorn made a furious push to catch Phil Mickelson, who started the tournament 67-65, but his 7-under 63 in the third round wasn't quite enough. Both players shot a 2-over 72 as Bjorn lost by one stroke.
Tiger Woods (2007)
Tiger became the second PGA Championship winner to shoot a 63. He started the second round six strokes off the lead but he was in first by Friday night after carding a 7-under 63 in the second round.
Tiger finished the weekend with a 1-under 69 on both Friday and Saturday to beat Woody Austin by two strokes.
Stricker took a two-stroke lead after shooting a 7-under 63 in the first round of the 2011 PGA Championship. He was 6-over Friday through Sunday as he finished tied for 12th at 1-under.
Jason Dufner (2013)
Dufner was the third PGA Championship to shoot a 63. He went 68-63-71-68 to win at Oak Hill in 2013 at 10-under, beating Jim Furyk by two strokes.
Hiroshi Iwata (2015)
Iwata is the most recent player to shoot a 63 at the PGA Championship, when he carded a 9-under 63 in the second round at Whistling Straights in 2015. His other three rounds were pedestrian – 77-70-71 – but his Friday performance was strong enough for him to finish T21 at 7-under.
He shot a 29 on the back nine, which is the second-best nine-hole score at the PGA Championship, and he nearly holed out on the 18th hole for the first-ever 62.