Beginning Sunday's final round with the tournament's largest-ever 54-hole lead of seven shots, Simpson held on tight during a one-over-par 73 to win by four strokes at eight under 270.

The American was seemingly on autopilot at one under in his closing round but showed he was human when found the water with his second shot at the difficult par-4 18th, resulting in a double-bogey.

He won from Charl Schwartzel, Jimmy Walker and Xander Schauffele, who all shot 67s to tie for second.

Simpson’s victory is his first in nearly five years and first since the ban on anchored putting. PHOTO: Sam Greenwood/Getty Images.

Simpson's triumph at golf's unofficial fifth major was all the more meaningful given it came almost five years after his last US Tour win.

"It means everything; I love this golf tournament," Simpson said.

The 32-year-old struggled after the January 2016 ban on anchoring the long-handled putter, which he used to win the 2012 US Open.

The North Carolina native also said he wished his father, Sam, who died last year after a battle with Parkinson's disease, could have witnessed an emotional fifth US Tour victory.

FINAL LEADERBOARD

"I thought about him all day. I think it's been an emotional week for my mum and sisters and my brother," Simpson said.

"We miss him like crazy, but I really wanted to do this for my mum."

Queenslander Jason Day bagged a share of fifth place with a 68 lifting him to 13 under.

Day mixed two early birdies with a holed bunker shot for eagle at the ninth, but his surge fizzled with an even par back nine.

Tiger Woods made a charge on Sunday at TPC Sawgrass before a bogey at the 14th halted his momentum. PHOTO: Richard Heathcote/Getty Images.

Meanwhile, Tiger Woods pulled out all the stops during his 69.

The 14-time major winner raced up the leaderboard, picking up six shots through 12 holes.

But a bogey at the 14th cruelled his charge before a double-bogey 5 at the par-3 17th dropped him to a tie for 11th at 11 under.

Also at 11 under was Adam Scott (68), while fellow Australian Marc Leishman struggled to a 76 to share 63rd at three under.

- Evin Priest, Australian Associated Press