Cayeux capped a breathtaking final round that featured seven birdies and an inward half of 29 by rolling in a 25-foot putt for eagle on the last hole, to finish the tournament at 20 under par, six strokes ahead of Keith Horne.
I asked Hendrik (Buhrmann) if hed like to finish before me, I just had a feeling that I was going to hole it. That was just the way my day was going. It was just one of those things.
Defending champion Andrew McLardy birdie the last three holes in a closing 67 that lifted him to 12 under for the championship and into a share of third with Nic Henning, who closed with a 68.
Ulrich van den Berg, Justin Walters, Richard Sterne and Hendrik Buhrmann finished in joint fifth on 11 under par.
Cayeux, who turned 27 last Tuesday, thus claimed the seventh Sunshine Tour victory of his career and third victory around the world in the past year, following his two victories on the Challenge Tour in 2004 that secured his European Tour card for the 2005 season.
Cayeux was unstoppable from the moment he birdied the very first hole at the Country Club Johannesburg and went on to add eight more without dropping a single shot, offering no room for hope to his pursuers.
Even when the ever-defiant Horne holed a 30-foot birdie putt on the 15th to get within three shots, Cayeux simply followed him in and added two birdies on the next three holes to set a new record for tied lowest final round score in Sunshine Tour history.
Ive been waiting for a round like this for a long time, said Cayeux. One where everything comes together. Ive been battling a bit with my putter but it all comes down to self-belief. The people close to me have really helped me get on with it too.