Kevin Chappell shot an 11-under 59 on Friday in the second round of A Military Tribute at The Greenbrier, to record only the 11th sub-60 round in PGA Tour history.
In doing so, the American equalled his compatriot Mark Calcavecchia's record of nine consecutive birdies in a round on the PGA Tour, set at the 2009 Canadian Open.
Chappell - playing in his first tournament since returning after 10 months out after back surgery - missed a 10-foot birdie putt on the par-four ninth at the course in West Virginia to fall a stroke short of Jim Furyk's Tour record.
The 33-year-old opened with a par at the 10th, then birdied the next eight holes to make the turn in 28, before adding further birdies at the first, fifth and seventh and is now 10 under for the tournament, having opened with a 71.
Furyk set the record in 2016 with a 58 in the final round of the Travelers Championship. It was the first sub-60 round on the PGA Tour since Brandt Snedeker's 59 at the 2018 Wyndham Championship.
Stuart Appleby shot 59 at The Greenbrier in the final round in 2010 to win by one stroke in its inaugural season.
Chappell's sub-60 round leaves him three strokes off the lead at the halfway stage, as Robby Shelton, Scottie Scheffler and Joaquim Niemann shared the 36-hole advantage.