Five ahead at the start of another humid day at Pinehurst Resort, the 29-year-old from Dusseldorf mixed two birdies with a lone bogey to reach the turn in one-under-par 34.
That left Kaymer at nine under for the championship, with American journeyman Erik Compton, a double heart-transplant recipient who has played mainly on the satellite tours, alone in second, also after completing nine holes.
Long-hitting Dustin Johnson was a further stroke back at two under after 11 holes, with compatriot Rickie Fowler (nine holes) and Swede Henrik Stenson (10 holes) level at one under.
However, the tournament was Kaymer's to win or lose as he headed into the final nine holes with a commanding lead after mixing aggressive golf when possible with careful recovery work as and when needed over the front nine.
Kaymer, watched by several LPGA Tour players including fellow German Sandra Gal and former women's world number one Yani Tseng as he teed off in the final round, did well to salvage par at the treacherous second hole.
After his second shot from a native waste area bounced over the back right of the green, he putted up to 10 feet and coolly sank the putt to stay at eight under.
The German then drove the green at the 313-yard, par-four third and narrowly missed his eagle attempt from 35 feet before tapping in for birdie to move six strokes clear at nine under.
Compton birdied the par-five fifth, two-putting from just short of the green, to trim Kaymer's lead to five and the German, playing one group behind, failed to follow suit there when he missed his birdie putt from six feet.
Though Compton faltered with a three-putt bogey from just 15 feet at the par-four seventh, Kaymer also went on to drop a stroke there after missing the fairway off the tee and failing to reach the green in two.
Compton went birdie-bogey to reach the turn in even par before Kaymer struck a superb eight iron to five feet at the par-three ninth and rolled in the birdie putt to stretch his advantage to six strokes.
- Sports & Recreation
- Erik Compton
- Rickie Fowler