Kim ran off eight birdies over his final 13 holes and set the course record at Congressional with 8-under-par 62, giving him a two-shot lead over tournament host Tiger Woods and two others.
The 24-year-old Kim has not won since his victory in the AT&T National last year, slowed by an assortment of injuries that caused his game to slip just as he was being anointed the next great American player.
It was the best round of his PGA Tour career, although Kim walked off the par-5 ninth green slightly perturbed after narrowly missing a 10-foot birdie putt. Apparently, eight birdies wasn't enough.
"You don't have many opportunities to bust a 61," Kim said.
But it was enough to hold off Woods, who missed his tournament last year after having season-
ending knee surgery. Woods played in the afternoon with deceptive wind swirling from trees lining the fairways.
He missed only two fairways and three greens, and made enough putts for 64, his lowest round since the 2007 Tour Championship.
"Today was nice to get back inside the ropes and get out there and try to catch AK," Woods said. "He lit it up this morning."
Bryce Molder, a former Georgia Tech golfer who can qualify for the British Open with a strong week at Congressional, is in the group at 64 which includes Woods and D.A. Points.
Former PGA champion Steve Elkington was another shot back on a day of exceptional scoring in relatively soft conditions from overnight rain in the Washington area.
"You can be so aggressive out there," Woods said. "You can fire at a lot of flags. The fairways got wide because it's not going to run out. If you get aggressive and get it going, you can post a number out there."
Three dozen players shots in the 60s, including Jim Furyk in the group at 66 and U.S. Open champion Lucas Glover at 69. Nearly half the 120-man field was at par or better.
Augusta native Charles Howell and Evans resident Vaughn Taylor were not among that group. They combined for 11 bogeys as Howell had 72 and Taylor shot 75. Howell offset his six bogeys with four birdies. Taylor had a double bogey to go with his five bogeys, but just two birdies.
As a tournament host, Woods took some solace in the fact that his 64 kept him close to Kim, who had already finished before Woods teed off.
"This is the day to pull it off," Woods said, "because the greens are so soft."