C.T. Pan carded a four-under-par 67 for a one-stroke triumph at the RBC Heritage after world number one Dustin Johnson fell apart in South Carolina.
Johnson – who was runner-up behind Tiger Woods at the Masters – led by one shot heading into the final round in Hilton Head but the American star capitulated as he posted a six-over 77.
The 2016 U.S. Open champion lost his way on the back nine, making three consecutive bogeys followed by back-to-back double bogeys en route to a tie for 28th position at four under.
Johnson's woes and Pan's impressive final round saw the Taiwanese player – who had five birdies and survived a bogey on the par-five 15th hole – clinch his maiden PGA Tour title on Sunday.
The 27-year-old Pan – who turned professional in 2015 – finished 12 under on the Harbour Town Golf Links, holding a one-shot lead with golfers still on the course.
Pan headed to the driving range to stay loose in the event of a playoff. But he sealed his first victory — he had a pair of wins in 2015 on the PGA Tour Canada — moments later when Shane Lowry's 180-yard approach shot sailed wide right of the 18th green.
He won ahead of American Matt Kuchar (67), with Lowry (70), Scott Piercy (69) and Patrick Cantlay (69) a shot further back.
"It's something when I was younger I always dreamed of," Pan told CBS. "I watched Tiger [Woods] playing growing up. To have a W on the PGA Tour means the world to me. It's a dream come true."
J.T. Poston (66), Seamus Power (67) and Kevin Streelman (68) ended up tied for sixth at 9 under.
Former world number one Jordan Spieth ended the tournament tied for 54th following his final-round 75.
After shooting a 74 on Saturday, Spieth went four over on day four to drop 12 positions to two over as his woes continued.