With his first two rounds at the 2017 Sony Open in Hawaii, Justin Thomas set the all-time PGA Tour record for the lowest 36-hole total in an event. Thomas shot 59 in the first round -- just the eighth sub-60 round in PGA Tour history -- and then backed it up with 64 to shoot 17-under 123 through the first two rounds at Waialae Country Club.
Thomas' mark passes the former record of 124, shot last by Jason Day at the 2015 BMW Championship with an 18-under total at Conway Farms near Chicago. That tied him with the 124 shot by Pat Perez on two different par-72 courses in the first two rounds of the 2009 Bob Hope Classic and David Toms, who did it at the 2011 Crowne Plaza Invitational on the par-70 Colonial Country Club course.
Thomas also matched the 54-hole scoring record, which is 188, first shot by Steve Stricker in the first three rounds of the 2010 John Deere Classic on the par-71 TPC Deere Run course.
The PGA Tour's 72-hole scoring record is 253, which Thomas shot en route to a 27-under total to win the 2017 Sony Open in Hawaii. His mark passed the 254 shot by Tommy Armour III at the par-70 La Cantera Resort course in the 2003 Valero Texas Open.
The Tour's scoring record in relation to par for a 72-hole event is owned by Ernie Els, who 31 under par on the par-73 Plantation Course at Kapalua at the 2003 Mercedes Championships in Hawaii. Jordan Spieth finished at 30 under par in an eight-shot win in the 2016 Hyundai Tournament of Champions on the same course.
(Steve Stricker owns the record for the most under par in the first 72 holes of a tournament, as he was 33 under par for the first four rounds of the then-90-hole Bob Hope Classic in 2009.)