South Korean Junghwan Lee produced his "best round" to delight a Genesis Championship home crowd at Woo Jeong Hills Country Club in Cheonan.
Lee fired a superb seven-under final round of 64 to finish at 11-under, three shots clear of England's Laurie Canter and Spaniard Nacho Elvira.
"I bogeyed the second hole but afterwards I grabbed (five) consecutive birdies and that really made the game easier and built momentum," Lee said.
"This was my best round, especially as the gallery out there were really cheering for me. They gave me the strength I needed.
"I just hope I can live up to their expectations in the future as well. I feel like I'm in a dream and still can't believe I won, so it's really hard for me to describe what I'm feeling."
Canter holed a monster putt from 100 feet on the 18th for a sensational eagle and a share of second. His 67 also included three birdies.
England's Andy Sullivan finished with a 70 to end tied-fourth with Italy's Andrea Pavan and Yuto Katsuragawa of Japan.
