The U.S. Open finalist became the first Briton to win four titles in a season. He will be the first Briton in the Open era since Fred Perry in 1936 to finish the year at No. 4.
Greg Rusedski and Tim Henman both reached No. 4 but never finished the year there and never won four titles and played in a Grand Slam final in one season.
Murray won in Doha, Marseille and Cincinnati. Mark Cox of Britain captured three titles in 1975.
"Gilles was hitting much better from behind the baseline, but I got a lot of free points from my serve,'' Murray said. "That was probably the key to my win today.''
Murray never faced a breakpoint and converted one in the fifth game to take the first set when Simon hit wide.
The Briton saved two set points in the tiebreaker before closing the match out when Simon hit into the net for his 30th unforced error. Simon had previously won five straight three-set matches.
"I couldn't move like I'm used to and Andy knew it, so he tried to kill me by making me run'' said Simon, barely able to walk the step up to the microphone. "Often I missed two easy shots, one after another. That's why I lost today, I couldn't focus on every point. It was too much effort for me.''
Murray beat Roger Federer in the semifinals, while Simon defeated top-ranked Rafael Nadal to reach his fourth final this year. Their victories denied a fifth Nadal-Federer final of 2008.
"I know you guys would have liked to have seen a Roger-Rafa final but you brought a great atmosphere, so thanks for coming,'' Murray told the crowd at the Madrid Arena, which hosted the tournament for the final time as it moves to the newly built "Caja Magica'' (Magic Box) next year.
The two finalists had both beaten Federer and Nadal this year, with Simon saving 17 breakpoint chances Saturday against Nadal.
The 16th-ranked Simon previously won at Bucharest, Casablanca and Indianapolis earlier this year and he is within reach of qualifying for next month's Masters Cup in Shanghai.
The 23-year-old Frenchman is ninth in the race to qualify for the season-ending tournament - seven points behind No. 7 David Ferrer and six back from Juan Martin del Potro in eighth and the final qualifying spot.
"It won't be easy because there are one or two tournaments left. I don't know if I play in Lyon because right now I just want to rest,'' Simon said. "You can't make any mistakes, you have to win. It won't be easy.''
Both players started tentatively with the match rarely venturing from lengthy groundstroke rallies on the baseline.
Murray led 15-40 in the fifth game. The Frenchman saved the first break chance but, after returning Murray's lob, his passing shot landed wide to leave him trailing 3-2.
Neither player looked anxious to up the tempo or come to the net unless necessary.
"I knew that he was going to be tired, but he plays so many matches like that you don't know how he is going to come out the next day,'' said Murray, who extended his winning streak over French opponents to 10. "When he was actually running he moved good and that was what was tough for me. I didn't expect him to chase as many balls down.''
Simon, who saved three break chances in the opening set, hit a winner down the far line to trail 4-3 but was missing often and Murray was rarely troubled on serve.
The 21-year-old Briton fired one of his 10 aces to clinch the first set.
"I didn't feel like I was on my game particularly, but I served great and came to the net a couple of times and took the ball on,'' Murray said.
The lethargic pace continued into the second set until the ninth game, when Murray volleyed at the net for one of 26 winners to set up a break opportunity. However, Simon saved it and a tiebreaker was required.
Simon repeatedly came to the net to reach Murray's drop shots. The rhythm picked up as Simon hit a crosscourt winner to complete a rally that put him ahead 6-4.
But Murray saved both set-point chances before setting up championship point when he forced Simon to lunge for another drop that the Frenchman couldn't return.
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