Memphis - Harris English fired back-to-back birdies at 16 and 17 on Sunday en route to a final-round 69 and a two-stroke victory in the US PGA Tour's $5.7 million St. Jude Classic.
English captured his first PGA Tour title with a 12-under-par total of 268 after four rounds on the par-70 TPC Southwind course.
He held off four-time major champion Phil Mickelson, who carded a 67 to share second place with Scott Stallings on 270.
Stallings, who closed with a 68, picked up four birdies on the front nine to seize the lead and led by as many as three strokes before a double-bogey six at the par-four 15th, where he was in the water.
He responded with a birdie at 16, but English moved past him with a two-putt birdie at 16 and an impressive birdie at 17, where he kept his approach shot under the trees and then drained a 17-footer.
The 23-year-old English had endured a difficult front nine that included four bogeys and just two birdies.
"I was feeling good about my ball-striking and just had to get those putts to fall," said English, who steadied himself with back-to-back birdies at the 10th and 11th.
"Harris played great coming down the stretch," Stallings said.
Mickelson, using the tournament as a tuneup for the US Open that starts on Thursday at Merion Golf Club in Pennsylvania, had three birdies in his last five holes.
He nearly holed his approach shot at 18, tapping in for birdie.
"I thought that one on 18 might even go," Mickelson said. "Looks like it wouldn't have been enough with Harris making birdie on 17. He's played some great golf."
Mickelson, who finished with five birdies and two bogeys, said the need for accuracy at Southwind was good preparation for the US Open, where finding the fairways will be crucial.
"I really like playing here," he said. "There's a real premium on hitting the fairway, then you can be aggressive into the greens."
And he was happy with the state of the game as he prepared for yet another attempt at the major championship in which he has finished runner-up five times.
"I'm hitting a lot of good iron shots," Mickelson said. "I had a little bit of trouble getting some of the putts and my pace was just off."
Ryan Palmer was alone in fourth place after a 67 for 271. It was a further shot back to Patrick Reed, who carded a 70 for 272.
Third-round leader Shawn Stefani struggled to a six-over 76, which dropped him into a share of seventh place on six-under 274, where he was joined by South African Rory Sabbatini (68) and Justin Hicks (69).
Leading final scores on Sunday after the fourth round of the $5.7 million US PGA Tour St. Jude Classic (USA unless noted, par-70):
268 - Harris English 66-64-69-69
270 - Scott Stallings 67-68-67-68, Phil Mickelson 71-67-65-67
271 - Ryan Palmer 72-67-65-67
272 - Patrick Reed 69-69-64-70
273 - John Rollins 67-71-67-68
274 - Rory Sabbatini (RSA) 69-69-68-68, Justin Hicks 67-69-69-69, Shawn Stefani 67-65-66-76
275 - Billy Horschel 71-69-68-67, Robert Allenby (AUS) 71-70-67-67, Glen Day 66-70-70-69, Camilo Villegas (COL) 69-68-69-69, Nick O'Hern (AUS) 68-71-67-69, Dustin Johnson 67-70-68-70, Jonathan Byrd 70-69-66-70, Padraig Harrington (IRL) 69-70-65-71
276 - Gary Woodland 69-72-71-64, Jason Bohn 67-70-71-68, Davis Love 66-70-71-69, Mark Wilson 70-71-66-69, David Hearn (CAN) 69-71-67-69, Doug LaBelle 70-66-70-70, Brendon Todd 69-71-66-70, Ben Crane 69-68-68-71, Roberto Castro 68-69-67-72