Jordan Spieth US Open 2015 Trophy
Jordan Spieth won the US Open title by one shot from Louis Oosthuizen and Dustin JohnsonReuters

Masters champion Jordan Spieth added another chapter to golf's record books with a nerve-jangling victory by one shot at the US Open on Sunday after a wildly fluctuating final round of high drama.

The American young gun sank a curling 28-footer to birdie the 16th and forge three ahead, then shrugged off a double-bogey at the 17th before becoming just the sixth player to slip into a green jacket and hoist the US Open trophy in the same year.

Though Spieth birdied the par-five last to close with a one-under-par 69, he then had to watch as fellow American Dustin Johnson, in the final pairing, had a 12-foot eagle putt to win it at the 18th.

Johnson's putt slid past the cup and he missed a four-foot birdie putt coming back to miss out on forcing an 18-hole playoff on Monday.

The 21-year-old Spieth posted a five-under total of 275 as he became the youngest winner of the US Open since Bobby Jones in 1923.

"I'm in shock," Spieth told Fox. "Wow. I watched it with [caddie] Michael [Greller] in there.

"I just wanted a fighting chance. I feel bad for Dustin. I had that feeling on 17. I'm just proud of the way we rebounded on 18."

Johnson, seeking his first major crown, had to settle for a share of second place with South African Louis Oosthuizen, who sensationally birdied six of the last seven holes, including five in a row from the 12th, for a 67.

Final Scores: -5 Jordan Spieth (U.S.), -4 Louis Oosthuizen (South Africa), Dustin Johnson (U.S.), -3 Adam Scott (Australia), Cameron Smith (Australia), Branden Grace (South Africa), -2 Charl Schwartzel (South Africa), -1 Brandt Snedeker (U.S.), Even Rory McIlroy (Britain), Jason Day (Australia), Shane Lowry (Ireland).