Spieth first teen to win on PGA Tour since 1931
Jordan Spieth parred the fifth playoff hole to capture the John Deere Classic, becoming the first teenager to win a PGA Tour event since 1931.
The 19-year-old American outlasted Canada's David Hearn and Zach Johnson in the marathon playoff for his first career title.
"I just told myself 'this is it and go for broke'. I am fortunate it ended the way it did," Spieth said. "Honestly I don't even know what to say right now."
Spieth closed with his third consecutive six-under 65 to tie Hearn (69) and Johnson (68) at 19-under-par 265 at the Deere Run course.
Spieth, who was the American Junior Golf Association's player of the year in 2009, birdied five of his final six holes, including a brilliant chip in from a greenside bunker at the 18th.
"The shot on 18 was the luckiest shot I ever hit in my life," said Spieth, who earned a place in next week's British Open.
Martin Flores fired an eight-under 63 during his final round to jump into a share of fourth place with third-round leader Daniel Summerhays (72) and Jerry Kelly (68) at 18-under.
The fifth playoff hole is where Johnson was all but eliminated after hitting his second shot into the water after all three players found the rough with their tee shots.
Spieth found the back fringe with his second shot and was able to two-putt for the victory while Hearn was unable to convert his seven-foot par putt.
"I don't know what I did to deserve those breaks. I said my prayers, I guess," said Spieth, who is 19 years, 11 months, 18 days old.
Johnny McDermott was the last teenager to win a PGA Tour event when he won the 1911 US Open at the age of 19 years, 10 months and 14 days.
Spieth, who played college golf at the University of Texas, earned a spot in the 2012 US Open as a replacement for Brandt Snedeker. He turned professional later that year.
He is the only golfer other than Tiger Woods to have won more than one US Junior Amateur, taking the title in 2011 and 2009.
Patrick Reed (67), Australia's Matt Jones (68) and J.J. Henry (69) shared seventh at 17-under 267 on Sunday.