Henrik Stenson claimed a share of second after a closing 65 and that moved him into first place in the Race to Dubai standings entering the Final Series.
American Daniel Berger also finished at 16 under after a closing 69, a shot ahead of then World Number Three Rory McIlroy and another American in Bill Haas.
Matsuyama followed in the footsteps of Isao Aoki - who won the European Open 33 years ago - and also became the first Japanese player to win an individual World Golf Championships event.
The victory was a continuation of some remarkable recent form with a win at the Japan Open and a second-placed finish at the CIMB Classic in the previous two weeks. Those results moved him into the top ten in the Official World Golf Ranking ahead of the tournament."Winning today, I feel has got me closer to being able to compete a lot better in the Major tournaments," he said. "My next goal is, of course, to win a Major and I'm going to do all that I can to prepare well for that.
Stenson shared the joint lowest round of the day with Matthew Fitzpatrick as he made seven birdies in a blemish-free effort. He made birdies on the second, third, sixth, seventh, 11th and 14th but when Berger made a gain on the 16th, he remained in second on the Race to Dubai.
An excellent putt from the fringe on the last then got him back into a share for second on the week and brought a fist-pumping celebration from the Swede.
Northern Ireland's McIlroy turned in 34 before four birdies in six holes from the 11th catapulted him up the leaderboard, before he saw a putt for a 65 lip out on the last.
Haas signed for a 69 with four birdies and a bogey.
Fisher finished in a tie for third here last year and had another productive week in Shanghai, making six birdies and two bogeys on Sunday, including a deflating dropped shot on the par five last.
Italian Molinari made four birdies and two bogeys, with Fowler joining Fisher in signing for a 68.
Garcia ended his week with a 67 while four bogeys in a row from the eighth in a closing 74 ended Scotsman Knox's challenge.
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