He kept the World Golf Championships event in English hands - Ian Poulter won it last year - with a convincing 3-2 victory over second seed Martin Kaymer on a nippy afternoon at Dove Mountain in Arizona.
Donald, the ninth seed, never trailed in any of his six matches and was clearly the best player over the week, as he showed with his dominance of German Kaymer, who nonetheless assumes the world No.1 ranking.
Donald, 33, collects $US1.4 million for his first victory in a WGC event.
“It feels amazing,” he said.
“I've had a bit of a monkey on my back the last few years. I haven't won for five years in the US and there's (been) a lot of sweat and tears to get to this point but I've broken through and it feels really good.
“I was a little shaky in the middle of the round. I held it together the last few holes and made nice birdies on 11 and 13 and 15 and that was good enough.
“My hat's off to Martin. Becoming No.1 in the world is quite an accomplishment and I guess it makes this win a little bit sweeter even.
Englishmen have dominated this event the past two years.
Poulter beat compatriot Paul Casey in last year's final.
Donald jumps to third in the world rankings, behind Kaymer and fellow Englishman Lee Westwood.
Donald was so dominant he did not need to play the 18th hole all week. He played fewer holes than any previous champion.
He took the lead in the final at the second hole and quickly went 3-up after five holes, before Kaymer fought back to all square at the turn.
But Kaymer showed he is human by missing a couple of short putts as Donald pulled away on the back nine.
Matt Kuchar won the match for third place with a 2 and 1 victory over fellow American Bubba Watson.
The course was covered by a couple of centimetres of snow after an overnight snowfall but it melted before play started on schedule, shortly after noon local time.
However, competition was briefly halted by a subsequent brief bout of sleet that eventually gave way to a sunny afternoon.
PHOTO -STUART FRANKLIN - GETTY IMAGES