JOHANNESBURG, 6 Dec 2014 (AFP) - Donald is on 13 under for the tournament with English compatriot Danny Willett keeping up the pressure in second place while first round leader Ross Fisher is a shot further back.
"I'm pretty pleased with the score. I could have played a little bit more solid on the back nine, but to be honest, around this course, with a lead, shooting 69, that's kind of what the game plan was, to go out and shoot a low round and keep myself ahead and in position for tomorrow," said Donald.
"I did that and felt pretty calm out there, and it was nice to finish with a three."
Willett's 65 was the best score of the day in Sun City and it could have been even better had he not missed a putt to draw level with Donald on the penultimate hole.
Third round scores in the Nedbank Golf Challenge at the Gary Player Country Club, Sun City, South Africa on Saturday (GBR/IRL unless stated; par 72):
203 - Luke Donald 71 63 69
204 - Danny Willett 71 68 65
206 - Ross Fisher 66 70 70
211 - Marcel Siem (GER) 68 72 71
212 - Louis Oosthuizen (RSA) 70 73 69, Thongchai Jaidee (THA) 71 70 71
213 - Kiradech Aphibarnrat (THA) 72 73 68, Miguel Angel Jimenez (ESP) 70 74 69, Tim Clark (RSA) 70 71 72
214 - Dawie Van Der Walt (RSA) 73 72 69, Alexander Levy (FRA) 68 70 76, Jonas Blixt (SWE) 71 73 70
215 - Stephen Gallacher 70 73 72, Tommy Fleetwood 74 67 74, Shane Lowry 72 72 71, Pablo Larrazabal (ESP) 73 71 71
216 - Charl Schwartzel (RSA) 70 71 75, Brendon Todd (USA) 73 68 75
218 - George Coetzee (RSA) 68 74 76
219 - Brooks Koepka (USA) 70 74 75, Marc Warren 75 73 71, Joost Luiten (NED) 72 74 73, Jaco Ahlers (RSA) 74 75 70
220 - Thomas Bjorn (DEN) 80 72 68, Martin Kaymer (GER) 74 75 71, Lee Westwood 72 70 78
222 - Kevin Na (USA) 77 73 72
226 - Mikko Ilonen (FIN) 76 78 72
231 - Danie Van Tonder (RSA) 77 78 76