Cape Town - Louis Oosthuizen, the last man to win the Open at St Andrews, birdied 18 to force his way into a playoff on Monday.
Zach Johnson, Marc Leishman and Oosthuizen will contest a four-hole playoff to decide the winner of the British Open at St Andrews on Monday.
They all finished with totals of 15-under 273 after Johnson and Leishman had 66s and Oosthuizen a 69.
It will be the first British Open playoff since Stewart Cink defeated Tom Watson at Turnberry in 2009 and the first three-way playoff since 1999 when Paul Lawrie triumphed.
Jordan Spieth meanwhile failed to become just the second player to win the first three majors of the year.
The 21-year-old American needed to sink a greenside putt at the last to get into the playoff, but failed to do so.
Spieth won the Masters in April and the US Open last month.
Ben Hogan in 1953 remains the only player in the history of the game to win the Masters, US Open and British Open in the same year.