The American responded to a strong challenge from Englishman Tyrrell Hatton to shoot a final-round 69 at TPC Sawgrass on Sunday and win with a score of 17 under.
Scheffler effectively secured victory with a run of five successive birdies from the eighth.
Hatton finished second on 12 under after a superb 65 that featured seven birdies in a course record-equalling back nine of 29.
Norway’s Viktor Hovland and American Tom Hoge finished on 10 under with Hideki Matsuyama, who briefly threatened Scheffler, on nine under.
Scheffler, who now supplants Jon Rahm at the top of the world rankings, had begun the day with a two-shot lead and was relieved to complete the job.
He said on
Sky Sports: “I did a really good job of staying patient, not trying to force things, and then I got hot in the middle of the round and tried to put things away as quickly as I could.
“The final stretch was pretty tough, especially with how windy it was getting. The shots on 17 were challenging. I am very thankful, relieved and a bit tired.”
Scheffler initially offered his rivals hope with a shaky start.
Playing partner Min Woo Lee canceled out his advantage within the opening three holes.
The Australian birdied the opener and then found himself in a share of the lead after Scheffler missed a short putt to bogey the third.
With Matsuyama on a charge further down the course to get within a stroke, the pressure was suddenly on the American.
Yet neither Lee nor Matsuyama could maintain their challenges.
The Japanese, who had shot up the leaderboard with seven birdies, took a double-bogey six at the 14th and then dropped another stroke on the last.
Meanwhile Lee made a mess of the fourth, first having to chip out of the rough and then taking a drop after finding water. He ended up with a triple-bogey seven and another seven on the 11th meant his tournament would finish in anti-climax on eight under.
Without finding his stride, Scheffler’s lead was back to three but there was still little room for error as Hatton was finishing strongly.
Hatton burst into life after the turn with his strong run including birdies on each of the last five holes to post a stern clubhouse target.
As he left the final green he was just two off the lead and may have sensed an unlikely victory opportunity.
“I just wanted to finish with as many birdies as possible,” Hatton told Sky Sports after wrapping up his round in style following a superb approach at the 18th from behind a tree.
“Fortunately I gave myself some great chances and the putter co-operated.”
It was at this point Scheffler rose to the challenge. He chipped in at the eighth to spark the run that all but wrapped up victory.
He dropped a shot at the 14th but never looked like relinquishing his grip and once he found the heart of the green at the ever-difficult 17th, the celebrations could almost begin.
Hoge, Hovland, Sungjae Im, Max Homa and Cam Davis all threatened to get into contention at various points but their chances faltered as Scheffler pulled away.
Englishmen Tommy Fleetwood and Aaron Rai, joint fourth overnight, simply struggled to find their spark. Rai had four bogeys and a double on the 17th – which he memorably aced on Saturday – in his 75 and finished on six under. Fleetwood was a shot further back after three bogeys and two doubles – also including the 17th – in a round of 76.
Justin Rose was never a contender but looked set for a decent finish until taking five at the 17th. That saw him drop back to eight under and an eventual seven-way tie for sixth place.
The 17th was not a nightmare for everyone, however, with Alex Smalley becoming the third player this week to make a hole-in-one at the signature par three.
His remarkable shot did not even touch the green as the ball bounced off the rough directly into the hole. He finished one over.