Fitzpatrick entered the final day on the Earth Course in a share of the lead but after starting his round with four birdies, he held a commanding lead and was on course to win the Race to Dubai.
Westwood birdied two of his last three holes to snatch solo second and be crowned European Number One but Fitzpatrick matched his 68 to finish at 15 under, one shot clear of his fellow Englishman at the top of the leaderboard, and win his first Rolex Series title.
Patrick Reed entered the week on top of the Race to Dubai Rankings presented by Rolex and remained there for much of the day but bogeys on the 16th and 17th saw him finish one shot away from being the first American to take Europe's season long honours at 13 under.
Fitzpatrick has been one of the European Tour's most consistent performers since coming through the Qualifying School in 2014, claiming five victories in his first four seasons, including at this event in 2016.
The last of those five was his second win at Crans-sur-Sierre Golf Club in 2018, and between then and this week, he had finished second five times.
He has now ended that run of frustration in emphatic fashion, sealing win number six in his 141st event and climbing back into the top 20 on the Official World Golf Ranking.
"The start I got off to, four birdies in the first four, five under through seven, it's a dream start," he said. "Fortunately I managed to pull away from that and really sort of create some distance.
"It was just obviously a bit of a grind on the back nine. For me it was just about finishing one hole at a time and just getting through it. So managed to do that and finished well.
"I had no idea about the Race to Dubai because I knew where I started the week at 16, a lot needed to go my way. When I saw Lee at second, it did enter my head briefly going to 18, even if I win it's probably not going to be enough, anyway. I just wanted to win a lot this week.
"I'm just trying to improve every year. I really set high standards of myself and I am honestly very hard on myself and my team will all tell you the same thing. To be here at 26, and I don't know what this win has taken me to in the world, potentially my highest year-end ranking, I'm very, very happy."
While all eyes were on Reed, he dropped a shot on the second to slip back and it was the final group of Canter and Fitzpatrick who took centre stage.
Both men hit nice approaches into the first, with Canter holing from 16 feet and Fitzpatrick finding the target from a quarter of that range before making a two putt birdie from a tricky position on the second green.
Canter holed from 20 feet on the third but again Fitzpatrick followed him in from from half the distance, and another ten footer on the fourth made it a four birdie start and a three shot lead as Canter dropped a shot.
At that point, Fitzpatrick was winning the Race to Dubai, but Reed holed a long putt at the fourth and put his tee shot to ten feet on the sixth to climb back onto the tie for second and to the top of the season-long standings.
A chip-in at the seventh from Reed cut the gap to two but Fitzpatrick got up and down from the sand on the same hole for a birdie of his own before making a gutsy par on the eighth as Reed missed an excellent birdie opportunity on the ninth.
A three putt on the 12th dropped Reed out of a share of second but he picked the shot straight back up from eight feet on the next and when he chipped in again at the 15th to sit second alone, he had tightened his grip on the Harry Vardon Trophy.
But he found sand off the tee at the 16th and dropped a shot, and Canter was the man who emerged as a potential kingmaker.
He had dropped a shot on the seventh but regained it on the eighth and also birdied the tenth before making a bogey on the 13th. But a two putt birdie on the 14th and a gain from eight feet on the next moved him into solo second and Fitzpatrick was once again in the box seat.
Westwood made birdies on the third, eighth and tenth but found water on the 14th before hitting a stunner into the 16th to set up a gain.
A birdie on the last after getting up and down from the sand put him in the clubhouse at 14 under and when Reed failed to do the same and dropped a shot on the 17th, both trophies were in Fitzpatrick's hands.
But two poor chips on the 17th saw Canter record a double bogey, meaning only an eagle up the last could deny Westwood at least solo second and the Race to Dubai title at 47 years of age.
Fitzpatrick bogeyed the 17th to see his lead cut to one but both he and Canter parred the last to ensure there would be double English celebrations at the season finale.
Reed chipped in again at the last to complete his 70, while Hovland carded six birdies and three bogeys in a 69.
Välimäki also made six birdies and three bogeys, while Canter signed for a 71 and Perez finished his week with a 68.