SOUTH AFRICA 10 Jan, 2015 (AFP) - World number 31 Schwartzel birdied the first four holes on his way to a third round of 66 to finish 13 under par, five strokes ahead of England's Matt Fitzpatrick and Scotland's David Drysdale.
England's Lee Slattery is a shot further back after posting the lowest round of the week with a 65, while halfway leader Andy Sullivan was one of eight players on six under after struggling to a 74.
Asked about the importance of winning his national Open for the first time, Schwartzel said: "In the big world people look at the Majors but coming from South Africa this is pretty much a Major for South Africans. It will be nice to go out and keep swinging the way I am tomorrow."
Fitzpatrick, 20, is seeking a maiden victory after gaining his card via Qualifying School.
His 67 on Saturday contained four birdies and an eagle in an inward half of 30.
"I'm delighted with the way I played today," the former US Amateur Champion said.
"I played good for the first six holes and just didn't make anything, but got it going on the back nine. From being two under at the turn to finish eight under was pretty special.
"Everyone's first aim is just to keep your card, particularly in my first year, but I am not setting my sights that I just want to make cuts to earn enough money to keep my card."
Leading scores following the third round of the South African Open at the Glendower Golf Club on Saturday (GBR/IRL unless stated, par 72):
203 - Charl Schwartzel (RSA) 68 69 66
208 - David Drysdale 68 72 68, Matthew Fitzpatrick 73 68 67
209 - Lee Slattery 70 74 65
210 - Lasse Jensen (DEN) 67 71 72, Paul Maddy 71 71 68, Jared Harvey (RSA) 71 69 70, Gary Stal (FRA) 75 66 69, Andrew Sullivan 66 70 74, Colin Nel (RSA) 68 70 72, Pablo Martin Benavides (ESP) 71 68 71, Richard Sterne (RSA) 67 74 69
211 - Jason Scrivener (AUS) 73 72 66, Thomas Aiken (RSA) 70 71 70, Branden Grace (RSA) 71 71 69, Rikard Karlberg (SWE) 70 70 71
212 - Alessandro Tadini (ITA) 71 68 73, Jj Senekal (RSA) 71 67 74, James Morrison 71 69 72
213 - Carlos Del Moral (ESP) 72 72 69, Hennie Otto (RSA) 72 71 70, Adilson Da Silva (BRA) 72 73 68, Matthew Nixon 72 69 72, Gareth Maybin 71 73 69, Jorge Campillo (ESP) 73 71 69, Matt Ford 70 71 72, Tjaart Van Der Walt (RSA) 70 73 70, Ernie Els (RSA 67 77 69
214 - Estanislao Goya (ARG) 74 69 71, Chris Swanepoel (RSA) 70 71 73, Jerome Lando Casanova (FRA) 70 74 70, Louis De Jager (RSA) 70 75 69, Doug McGuigan (RSA) 73 70 71, Edoardo Molinari (ITA) 69 76 69, Neil Schietekat (RSA) 74 72 68