The 46-year-old ended a four year winless drought on the European Tour with his victory at the 2018 Nedbank Golf Challenge hosted by Gary Player, and a triumph at Abu Dhabi Golf Club would be his 25th - over 23 years after his first.
That would make him just the third player to win European Tour events in four different decades after Mark McNulty and Des Smyth, but he had a young fellow Englishman chasing him down in Matthew Fitzpatrick.
Westwood turned in 32 to get to 18 under, two shots clear of Fitzpatrick, who had completed ten holes.
Fitzpatrick took advantage of the par five second to get within one but Westwood did the same after laying up to maintain his cushion.
A long putt on the third had Fitzpatrick at 14 under and when he played a stunning tee shot to three feet at the par three fourth, there was a tie at the top.
Westwood holed from similar range on the third to edge ahead again and made a good up-and-down from the sand on the fourth to stay at 16 under.
Birthday boy Fleetwood was making a charge through the field and he birdied the first and second before playing an excellent tee shot into the fourth.
He followed a 15 footer at the seventh by taking advantage of the par five eighth and was five under through eight holes, just three back.
An approach to ten feet on the ninth saw him turn in 30 but he stayed three back as Westwood put an approach to six feet from a bunker at the fifth.
Fitzpatrick missed good birdie chances at the sixth and seventh but got up and down from the sand on the par five eighth to trim the lead back to one.
Westwood was not in the mood to be caught, however, and he laid up on the eighth and put his approach to six feet for another gain.
Oosthuizen was a long way back as he turned in 34 with birdies on the fourth and eighth but he took advantage of the tenth and holed long putts on the 11th and 12th to surge up the leaderboard.
Kaymer is a three time winner of this event and after holing out with his second for an eagle on the ninth, he never looked back, birdieing the tenth, 12th, 13th, 17th and last in a 65, a score matched by Jamieson.