Young made two eagles on par fours in his third round on Saturday, holing out with a wedge from 142 yards on the third hole and driving the 280-yard 15th to within four feet.
It was the 13th sub-60 round since Al Geiberger first shot golf's 'magic number' at the 1977 Memphis Classic.
Scottie Scheffler had been the most recent, at the TPC Boston in 2020 at The Northern Trust.
"I can't say I was expecting it," Young said.
"I've been playing better than the results have shown (but) waking up this morning, I wasn't really thinking, 'I'm going to be five under through four'.
"It was a lot of fun to do."
His remarkable round didn't even get Young the distinction of the course record at the TPC River Highlands - Jim Furyk shot a 58 in 2016 at the Travelers, the lowest round in PGA Tour history.
Young still moved from a tie for 43rd to equal-10th, five shots off the lead.
Jordan Spieth became a footnote in history as the only PGA Tour player to twice play with someone who shot 59.
Spieth was in the group with Justin Thomas when he carded the same score in the opening round of the 2017 Sony Open.
He could have gone even lower. After his eagle on the 15th, Young hit his tee shot to within seven feet on the par-three 16th but missed the short birdie putt.
On the closing hole, needing birdie to tie Furyk's record, his drive settled on the steep face of a fairway bunker and Young was unable to get it on the green.
He still made par for the seventh round of 59 or lower this year on tours around the world.
"To have a day like today where things start going in, and it feels like your reward for good shots, it leaves me with a good taste in my mouth," Young said.
He finished at 13-under and was tied with Tom Kim, who was watching some of Young's round on a video screen at the practice range as Kim was getting ready for the start of his third round.
Kim shot a 65 and led by one over Scottie Scheffler and Akshay Bhatia.
The other six rounds at 59 or lower this year include Joaquin Niemann on LIV Golf and a record-tying 57 by Cristobal del Solar on the Korn Ferry Tour in Bogota, Colombia.
