In pursuit of his second major title, the 29-year-old German conjured a miraculous eagle at the par-five fifth on the way to a two-over-par 72 in blazing sunshine at Pinehurst Resort where scoring was at its most difficult for the week.
With very little margin for error on approach shots into domed greens running increasingly fast and firm, Kaymer bogeyed two of his last six holes but sank a six-foot birdie putt at the 18th for an eight-under total of 202 in the year's second major.
"Two-over par is not as bad as it looks on the scorecard," the former world number one told reporters. "I kept it very well together, even though I didn't hit as many great shots as yesterday and Thursday. Overall it's a decent round.
"They put the pins in very, very tough positions. I think 18 was the only pin where you could be aggressive. The other flags, if you hit it to 25 feet, it was a good shot.
"I didn't hit many fairways today, so the challenge tomorrow will be to keep going and not try to defend (the lead). If you try to defend, then you don't swing as free."
Kaymer, a commanding six strokes clear overnight after setting a U.S. Open low for 36 holes with a 10-under aggregate of 130, finished five ahead of Americans Rickie Fowler and Erik Compton, whose 67s were the best of the round.
Swedish world number two Henrik Stenson and long-hitting American Dustin Johnson were a further shot back at two under after carding 70s on a day when Fowler and Compton were the only players in the 67-man field to dip under par.
"Very, very pleased with today's work," Fowler told reporters after a five-birdie display on a day when the average score was 73.82. "I kept it in play and stayed out of trouble when I could.
"I can put myself in contention with the rest of the group, and see what Martin does," Fowler said of Sunday's final round.
"If he goes out and posts double digits (under par), it's going to be impossible for us to catch him. It's like a second tournament going on."
Reigning U.S. Open champion Justin Rose of England inched his way back up the leaderboard with an even-par 70 to end what is traditionally known as 'Moving Day' at the majors at one over, nine strokes off the pace.
Australian world number one Adam Scott (73) and 2011 winner Rory McIlroy (74) did not fare as well as they finished a further two shots back at three-over 213.
Tricky pin positions, many of them tucked away in the corners of Pinehurst's infamous turtleback greens, and increasingly slick conditions presented a daunting challenge for the players in the third round.
Kaymer, seeking his second major title after winning the 2010 PGA Championship, made his first bogey at the treacherous par-four second where he three-putted from long range, just off the front of the green.
That dropped him back to nine under, but still six strokes in front after playing partner Brendon Todd also bogeyed the hole.
Kaymer narrowly missed a birdie opportunity from nine feet at the third, then did well to drop only one stroke at the par-four fourth after taking an unplayable lie when his tee shot ended up next to a pile of pine needles.
He punched a low third shot down the fairway, well short of the green, struck his fourth to 15 feet and coolly sank the bogey putt before pumping his fist with relief.
With his lead cut to five strokes, Kaymer appeared to be in trouble at the fifth when his tee shot sailed left into a native waste area behind a small bush.
From there, however, he brilliantly struck a high draw to six feet and sank the eagle putt to get back to 10 under, seven ahead of his closest pursuers.
Kaymer again stumbled with a three-putt bogey at the difficult par-three sixth, where his first putt rolled off the edge of the green, before he parred the next three holes to remain at nine under.
The German dropped further shots at the par-four 13th, where he three-putted, and at the par-three 15th, where his tee shot ended up just short of the green, but his birdie at the last earned him extra breathing room with a five-stroke advantage.
- Sports & Recreation
- Rickie Fowler