Martin, who trailed by one stroke entering the final round, charged to a five-shot lead on the front nine but then stumbled down the stretch and nearly surrendered his advantage before hanging on for a two-stroke victory at Leopard Creek Country Club in South Africa.
Martin sealed with win with a birdie at the last hole, finishing at 11-under 277.
Third-round leader Anthony Michael fired a round of 1-over 73 to share second place with Charl Schwartzel (70) and Thorbjorn Olesen (66) at minus-9.
Sole possession of fifth place at minus-7 went to Thomas Aiken while Alex Haindl (73) and Robert Dinwiddie (70) ended knotted in sixth place at minus-6.
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