SOUTH AFRICA 11 Jan, 2015 (AFP) - The 2011 Masters champion Schwartzel looked to be heading for victory, with the South African entering the final round at the Glendower Golf Club in Ekurhuleni five strokes clear of the field.
The world number 31 still had a four shot cushion with five holes to go.
But he then folded dramatically, dropping a shot at the 14th, and three-putting the 16th for a double bogey.
A poor tee shot at the 17th triggered another bogey to leave him level with Sullivan at 11 under par.
Sullivan held his nerve when the pair returned to the 18th for the first sudden death hole.
Both players failed to make the fairway, with Sullivan recovering brilliantly from the trees to hole out from 10 feet for a winning birdie.
Sullivan had begun the final round seven shots behind his playing partner Schwartzel, but set up his maiden win on the European Tour with four birdies, an eagle and one bogey for a closing 67.
"It's unbelievable," said the 27-year-old.
"After Saturday I didn't think I stood much of a chance with Charl getting ahead that far.
"I just dug in there yesterday and today and found myself in a position where I had a chance to win. My caddie said over the last few holes 'no regrets' and I've definitely got no regrets over the last few holes, especially that play-off hole.
"Charl has won major championships, my caddie said expect him to hole (his third shot) and he nearly did. I was delighted just to hit the green and have a chance to win and I'm just glad I took it.
"I didn't want to give him a second chance to take the title away from me so I am absolutely delighted and I hope the guys at Nuneaton Golf Club are having a few beers for me!
"To just play on the European Tour is something I've wanted to do my whole life, so to win an event just caps it all off and to do it in South Africa where I have always enjoyed playing, it has just been an incredible week."
England's Lee Slattery carded a closing 69 to finish third, one shot outside the play-off, with Spain's Pablo Martin another shot back in fourth after also recording a 69.
Leading scores following the fourth round of the South African Open at the Glendower Golf Club on Sunday (Gbr & Irl unless stated, par 72):
277 - Charl Schwartzel (RSA) 68 69 66 74, Andrew Sullivan 66 70 74 67
Sullivan won first hole of play-off
278 - Lee Slattery 70 74 65 69
279 - Pablo Martin Benavides (ESP) 71 68 71 69
281 - Thomas Aiken (RSA) 70 71 70 70, Alessandro Tadini (ITA) 71 68 73 69, Paul Maddy 71 71 68 71, Jared Harvey (RSA) 71 69 70 71, Gary Stal (FRA) 75 66 69 71, Matthew Fitzpatrick 73 68 67 73
282 - Jason Scrivener (AUS) 73 72 66 71, David Drysdale 68 72 68 74
283 - Hennie Otto (RSA) 72 71 70 70, Raphael Jacquelin (FRA) 69 76 72 66
284 - Branden Grace (RSA) 71 71 69 73, Rikard Karlberg (SWE) 70 70 71 73, James Morrison 71 69 72 72, Neil Schietekat (RSA) 74 72 68 70, Trevor Fisher Jnr (RSA) 72 73 71 68
285 - Carlos Del Moral (ESP) 72 72 69 72, Lasse Jensen (DEN) 67 71 72 75, Ernie Els (RSA) 67 77 69 72, Matthew Nixon 72 69 72 72, Richard Sterne (RSA) 67 74 69 75
286 - Alex Haindl (RSA) 73 72 71 70, Adilson Da Silva (BRA) 72 73 68 73, Jorge Campillo (ESP) 73 71 69 73, Matt Ford 70 71 72 73, Andrea Pavan (ITA) 74 71 71 70, Niclas Fasth (SWE) 69 73 73 71, Colin Nel (RSA) 68 70 72 76, Rhys West (RSA) 75 71 71 69