South Korea's Kim Si-woo moved within sight of his first major after Sam Burns' two-shot overnight lead at the British Open vanished with three consecutive bogeys.
World number four Cameron Young set the clubhouse lead at nine under par, but defending champion Scottie Scheffler and home favourite Tommy Fleetwood fell away after bright starts to the final day at Royal Birkdale.
Burns is aiming to end his wait for a first major and looked composed when he birdied the second hole to extend his lead at 11 under par.
However, the world number 18 began to unravel at the par-three fourth and did well to escape with dropping just one shot on the fifth before another bogey followed a wayward drive on six.
Kim, who began the day two off the lead, took advantage as he birdied five and six to edge ahead.
A four-time winner on the PGA Tour, Kim has only once finished in the top 10 at 37 previous major appearances.
Young stormed through the front nine in 29 shots to go from three under to eight under par and added more birdies at the two par fives on the 14th and 17th coming home to move into a share of the lead at 10 under.
However, he found the sand off the tee at 18 and smashed his second shot into the face of the bunker for a bogey that could cost him the chance of a first major.
New Zealand's Ryan Fox, Australian Lucas Herbert and Burns are all two off the lead heading onto the back nine.
Scheffler's defence of the Claret Jug has been blighted by poor putting.
The world number one began the final round six back, but halved that deficit with three birdies in his opening five holes.
But after another birdie at the 12th, bogeys at the 13th and 15th left the American with too much to do in his final three holes.
Just a stone's throw away from where he learned to play the game in Southport, Fleetwood's fast start delighted the home fans.
The world number nine was three under for the day through eight holes to close to within one of the lead.
But the wait since 1992 for an English winner of the British Open is set to continue after three consecutive bogeys dropped Fleetwood back to where he started the day at five under.
Rory McIlroy was never truly in contention to land his seventh major and ended with a 71 to finish at one under par for the tournament.
"Any time I got a little bit of momentum out there, I seemed to make a bogey," said the world number two. "Just one of those weeks I couldn't get it going."
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