Donald in command in Dubai
Luke Donald took control of the DP World Tour Championship in Dubai by going to the turn in 32 - and had still to drop a stroke all week.
Birdies at the second, third, seventh and ninth lifted England's world number two to 15 under par in the European Tour's season-ending event.
He led by two from South African Louis Oosthuizen, while world number one Rory McIlroy was in a group three behind.
McIlroy and Scot Marc Warren shared the overnight pace with Donald, but they had early troubles.
The Northern Irish star put his opening drive into sand and bogeyed, then had to work hard for a par on the 583-yard next after pulling his tee shot into the bushes.
Warren, 189th in the world, did the same and after being forced to take a penalty drop - McIlroy was able to hack out - ran up a bogey six.
He was still searching for his first birdie of the day after nine holes, but McIlroy did at least come back with birdies on the third and short sixth.
Donald, trying to become the first player to win a tournament on the circuit without a bogey since Jesper Parnevik in 1995, sank 10-foot putts at the second and third, chipped close on the long seventh and then finished the outward half with his fourth birdie.
He was in danger of making his first mistake on the next, but after splashing out of a greenside bunker to 10 feet he made the par putt.
Last year's Masters champion Charl Schwartzel had actually overtaken him when his second to the seventh ran up a slope and then back down close to the flag for a tap-in eagle, but he followed that by three-putting the eighth and then bogeyed the 10th as well.
Former Open winner Oosthuizen moved into second place with a hat-trick of birdies from the seventh.
Earlier Indian Jeev Milkha Singh became the seventh player to have a course record 64, missing a 15-foot chance to set a new mark on the final green. The round lifted him from one over to seven under.
Donald remained bogey-free after 48 holes, but McIlroy joined Oosthuizen only one behind by holing putts of nine and 14 feet at the 11th and 12th.
Donald was twice in the rough on the long 14th, but then pitched to 10 feet and made it for his fifth birdie and a two-shot lead again.
That quickly disappeared, however, as McIlroy found the green in two and knocked in a putt of around 30 feet for eagle.
Golf's top two were locked together at 16 under, two ahead of Oosthuizen and three clear of Schwartzel.