BOSTON (AFP) - Rory McIlroy shot a superb six-under-par 65 to end his 16-month PGA Tour title drought with victory in the Deutsche Bank Championship on Monday.

The Northern Ireland star laid the foundations for a two-stroke victory over England's Paul Casey with a bewitching front nine performance, sinking five birdies to be five under at the turn.

Two more birdies and a bogey on the back nine at TPC Boston sealed a deserved win for the 27-year-old, whose last win on the PGA Tour came at the Wells Fargo Championship in May 2015.

The win earned McIlroy another $1.53 million (S$2.08 million) and will see him move up to third in the next set of world rankings.

It also catapulted him from 38th to fourth place in the standings for the lucrative FedExCup post-season series.

Third round leader Casey had begun the day three shots clear, but saw his challenge unravel after posting four bogeys in a two-over-par 73 to finish second.

PGA champion Jimmy Walker finished three adrift of McIlroy after shooting a 70.

Australia's world number six Adam Scott was alone in fourth place after a six-under-par 65, but had left himself too much work to do to challenge for the lead.

Patrick Reed, James Hahn and Argentina's Fabian Gomez all tied for fifth place, 10 under for the tournament, five behind McIlroy.

US Open champion and world number two Dustin Johnson recovered from his disastrous third round 75 with a 66 to claim a share of eighth place with six others players at nine under.

World number one Jason Day finished with a closing 67 in a six-way tie for 15th at eight under.