Golf: Louis Oosthuizen holds one-shot lead over Collin Morikawa heading into final round of The Open Championship

South African Louis Oosthuizen held his nerve to lead the British Open by one shot after a gripping third round played out in bright sunshine at Royal St George's on Sunday (NZ time).

Oosthuizen, the 2010 Open champion, had moved serenely to 13-under with a birdie on the ninth hole before two bogeys, his second and third of the tournament, halted his progress.

Americans Jordan Spieth and Collin Morikawa joined him in a three-way tie for the lead but Oosthuizen then sank a 10-foot birdie putt on the 16th to move back to the top of the leaderboard and carded a 69 to finish at 12-under.

"Definitely wasn't swinging freely today, was a little all over the place with my iron shots," Oosthuizen told Sky Sports.

"The R&A weren't happy with the low scoring and they put some pins out there that were very questionable, but it was tough and I'm glad I could hold it together."

Oosthuizen, 38, has finished second in six major championships since his triumph at St Andrews 11 years ago.

"I'm very excited, it's a great position," he said.

Morikawa emerged as Oosthuizen's closest challenger, recovering from a poor start to collect four birdies and sign for a 68 that left him on 11 under.

Spieth, bidding to lift the Claret Jug for the second time, racked up four early birdies and another one at the 10th took him to 12 under.

The 27-year-old's putter went cold on the back nine, however, a dropped shot at the 11th halting his momentum before he bogeyed the last two holes in a round of 69 to finish at nine under.

New Zealand's Ryan Fox dropped down into a tie for 25th with a third round score of one-over. 

He sits at three-under after the third round, and sits nine shots behind Oosthuizen at the top of the leaderboard.

Fox is the only Kiwi left in the field, as 22-year-old Daniel Hillier failed to make the cut after the second round.