English birdied the 16th and 17th holes to notch a final-round 1-under-par 69, finishing at 12-under-par 268.
He became the seventh Memphis winner in eight years to come from behind in the final round.
Phil Mickelson was in contention until the end, birdying the final hole for a 3-under 67. But he came up short, finishing one shot back at minus-10 along with Scott Stallings (68).
Grabbing sole possession of fourth place was Ryan Palmer (67) at 9-under 271. Patrick Reed (70) ended alone in fifth at minus-8.
Third-round leader Shawn Stefani stumbled into a share of seventh one shot further back after carding a 6-over 76.