The Northern Irishman, who was one-down through seven holes, rallied on the back nine to take one of the most sought after titles on the European Tour.
A birdie on 12 and a crucial par on 14 gave McDowell the lead for the first time in the match. Another birdie at 15 put him two-up allowing him to halve both 16 and 17 to hold on for the match.
"It's very special," said McDowell, following his victory.
"We have been talking all week about how prestigious this event is. I can't say how excited I am to win it and add my name to that list of legends."
Former champions of the prestigious event include major winners, Ernie Els, Jack Nicklaus, Arnold Palmer, Gary Player and Seve Ballesteros.
The win takes McDowell up to the top of the European Tour's Race to Dubai points list. The Ulsterman will also pull on his golf clothing next week at the BMW PGA Championship at Wentworth as the seventh ranked golfer in the world having jumped ahead of South Africa's Louis Oosthuizen.
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