The 26-year-old American found himself behind early on against Young but responded brilliantly, winning four holes in a row from the fifth to turn the match on its head.
He kept his foot on the gas after the turn, with wins at the tenth and 12th stretching his lead to five.
And the contest ended at the 13th as Burns' eighth birdie of the match wrapped up a convincing win.
Burns said: "What a week. I’m so tired. I felt like I found something towards the end of my match with Scottie and was able to carry that on this afternoon.
"It means a lot. I've been in a play-off in a WGC before and I ultimately did not get it done.
"So to have the opportunity today - very honoured to have that opportunity to compete against Cam, who is one of the best players in the world. I'm very pleased."
Rory McIlroy came out on top in his heavyweight clash with World Number One Scottie Scheffler in the consolation match, winning 2&1 to finish third.
Young drew first blood in the final, winning the second hole with a birdie.
But Burns came roaring back, turning a one-hole deficit into a commanding lead by winning the fifth, sixth, seventh and eighth to go three ahead.
And a 12-foot birdie on the tenth saw Burns go 4UP, with Young running out of holes to turn things around.
Burns looked set to increase his lead at the 11th after converting his 24-foot birdie putt but Young followed him in from 22 feet to tie the hole.
But after Young sent his second shot into the water at the 12th, Burns went 5UP with just six holes remaining.
And with Young finding the water again on the 13th, Burns made yet another birdie there to secure his fifth PGA TOUR title.
Young focused on the positives following his defeat in the final.
He said: "I think I probably shot about 35 under par for the seven rounds. Obviously frustrating to lose today, but I definitely played a lot of good golf and I think my game's in a really good spot for the next few weeks."
Earlier in the day, Burns had beaten his close friend Scheffler in a back-and-forth semi-final encounter which was decided at the third play-off hole.
Young, meanwhile, beat McIlroy at the first extra hole in their evenly-matched contest. DP World Tour
Sam Burns storms to victory
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