• The Australian's bogey-free round featured a brilliant chip-in for birdie at the 12th hole.
• It is the former world number one's 13th PGA Tour title but first since the 2018 Wells Fargo Championship.
Jason Day claimed his first PGA Tour title in five years by winning the Byron Nelson in Texas.
Day, 35, hit a nine-under final round of 62 to finish on 23 under overall, one stroke ahead of South Korea's Kim Si-woo and American Austin Eckroat.
The Australian's bogey-free round featured a brilliant chip-in for birdie at the 12th hole.
It is the former world number one's 13th PGA Tour title but first since the 2018 Wells Fargo Championship.
"It's been a struggling few years, five years since our last win," said Day, who won the 2015 PGA Championship.
"The way I played today was really special. I'm very pleased and happy with how things have progressed over the last couple of years."
Day said "just trying to get through a tournament was difficult" because of back injuries overs the years since his previous victory.
He added: "To be on the other side of it, to be healthy, winning again. It's so good to be on the other side."
Day won his first PGA Tour title at the 2010 Byron Nelson, then held at a different course in Dallas.
He started the final round at TPC Craig Ranch in McKinney in a tie for fourth, two shots behind the leading trio of Eckroat, Ryan Palmer and Zecheng Dou.
He hit four birdies on the front nine to move into a share of the lead, taking it outright with his sublime chip on the 12th.
Kim, who shot a fine round of 63, birdied the final hole to move to 22 under, with Day knowing he needed to also find a birdie to avoid a play-off.
A superb approach shot gave Day a simple two-foot birdie chance which he duly converted to take the clubhouse lead.
His victory was confirmed when Eckroat could not hit an eagle on the last.
Day will look to win his second major title when this year's PGA Championship in New York begins on Thursday.
World number two Scottie Scheffler, who started the final round level with Day, threatened with four birdies on the front nine.
But he could not keep up the pace, carding a six-under 65 to finish in a tie for fifth alongside England's Tyrrell Hatton and China's Dou.