British Open hopefuls Scott Jamieson, of Scotland, and Mark Tullo, of Chile, finished in a seven-way tie for third.
However, it was 203rd-ranked Jamieson, a former Augusta State golfer, who made a birdie at the last hole to secure the available qualifying spot for the year's third major - by virtue of having a higher ranking than Tullo by 29 places.
"It was the first putt I had all day that I was really confident on my read, and it just reached the hole," said Jamieson, who will play at his first major. "It's not registered yet, to be honest."
Donald, a 33-year-old Englishman, started the third and final round a shot behind a trio of joint leaders but rolled in nine birdies in a majestic bogey-free display at Castle Stuart.
With only a light wind leaving the links course defenseless, Donald romped home with a winning total of 19-under, ahead of Sweden's Fredrik Andersson Hed (62).
His eighth professional title - and third this year - didn't just cement his top ranking, which he secured for the first time nearly two months ago by beating compatriot Lee Westwood in a playoff for the PGA Championship on his last appearance in Europe.
It also provided the ideal tonic ahead of the British Open at Royal St. George's starting Thursday, where he'll attempt to land his first major.
Champions Tour: In Pebble Beach, Calif., Jeff Sluman shot 2-under 70 and overcame a pair of bogeys on the back nine, holding on to win the First Tee Open for the third time.
On a day when most of the leaders struggled just to break even, Sluman had five bogeys and closed with three consecutive pars to finish at 10-under 206 and seal his first victory since winning here in 2009. He also took the title at Pebble Beach in 2008, making Sluman the only three-time winner of this event.
Jay Haas entered the final round with a two-stroke lead, but struggled all afternoon and had 75 to finish in a three-way tie for second. David Eger (72) and Brad Bryant (73) joined Haas at 208.