The world number one becomes the first Briton to win the title since Sir Nick Faldo in 1990. The 34-year-old's PGA Tour peers voted him in after an incredible year which was capped after he won the Race to Dubai title on Sunday with a third-place finish.
This year Donald has had 14 top-10 finishes in 19 PGA Tour event starts, finishing ahead of Americans Keegan Bradley, Bill Haas, Webb Simpson and Nick Watney in the players' poll.
He said: "It's obviously been a tremendously consistent year for me. It's not easy to be a member of both tours and do what I've done.
"There's only really a handful of people that do it, so obviously there's a limited number of people that can do it in any one year.
"To be the first is very special, and I think it's probably my greatest achievement this year."
Bradley, who won the US PGA Championship in August, was awarded the Rookie of the Year title.
He said: "I'm thrilled to win Rookie of the Year for all that it means, but also most importantly the fact that it was voted to by my peers.
"It's an award that you can only win one time in your entire career.
"You get one chance at it, and it was the main goal of mine to start the year and it's a huge honour and privilege to be the Rookie of the Year this year."
