Fowler kicks off 2016 by breaking into golf's top 4
Fowler fired a final-round 68 to finish on 16 under par, one shot ahead of Belgian Thomas Pieters.
Northern Ireland's Rory McIlroy tied for third alongside Sweden's Henrik Stenson a further shot away, while Spieth shot 68 in his final round to secure a tie for fifth.
Fowler's rise up the rankings comes on the back winning the Players Championship, the Scottish Open, the Deutsche Bank Championship within the last 12 months, with this latest success marking him down as a genuine challenger to the established top three of Spieth, Jason Day and McIlroy.
"I want to be playing against the best players in the world and beating the best players in the world," said Fowler. "I'm looking forward to going into battle with those guys all year long and for the rest of our careers.
"The ultimate goal this year is to go win a major and this is a step in the right direction for sure. It's nice to have that added confidence now, really having the belief and knowing that, come Sunday when I'm in the mix, I know I can go get it done.
"This is a great way to start 2016. It is nice to have the game where it's at right now going into the season, instead of trying to work on things and trying to find stuff."
Now coached by Tiger Woods' former mentor, Butch Harmon, Fowler displayed all of his countryman's battling qualities during his final round.
He saw a four-shot lead cut to two after double-bogeying the seventh, but bounced back by eagling the eight from a green-side bunker.
McIlroy's 35ft putt on the last closed the gap to one, but Fowler replied by chipping in from off the 17th green to extinguish the Irishman's hopes.
McIlroy welcomed Fowler's recent emergence: "Everyone is talking about the big three and Rickie sort of needing to do something but, if the four of us are top four in the world, it's a nice narrative going into the meat of the golf season," he said.
Spieth's second round 73 cost him any chance of victory, with the American suggesting tiredness may have played its part.
"We are kind of beat up mentally," he said. "Physically, we're not 100 percent right now. It shows in certain places, and this week, the first day I was here, I was striping it and since then, I was just a little weak.
"I didn't make anything on the greens. Sometimes that happens and we kind of ground out eight-under on the weekend in what really could have been something special but it also could have been worse."