Donald has exchanged the top spot with the Northern Irish star and reigning US Open champion for the past two months.
The Englishman needed a top-seven finish this week to secure the top ranking once more. With a birdie on the par-5 18th to complete a final-round five-under par 67, Donald finished 72 holes on 17-under 271.
In a bogey-free final round, Donald birdied the par-3 third and ninth holes on the front side and added birdies on the par-5 11th and par-4 13th before his concluding birdie, which avoiding him sharing third with two rivals.
Two weeks ago at the US PGA Heritage Classic, Donald finished in a share of 37th place when he needed to finish eighth or better to keep idle McIlroy from passing him for the top ranking.
McIlroy had moved to World No. 1 for the first time in his career last month.