La Quinta, California - US golfer Nick Dunlap won The American Express tournament by one shot to become the first amateur to take home PGA glory in 33 years.

The victory makes Dunlap the first amateur to win on the PGA Tour since Phil Mickelson back in 1991.

The 20-year-old University of Alabama student sank a birdie putt at the par-five 16th to equal the lead of fellow US player Sam Burns at the Pete Dye Stadium Course in La Quinta, California.

Burns then stumbled on the day's toughest hole, finding water off the tee at the par-three 17th.

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At that time, Dunlap was on the green 35 feet from the hole.

He went on to make a routine par, while Burns came out with a double bogey.

The amateur took the lead with the par-four 18th remaining, while on the 18th green, South Africa's Christiaan Bezuidenhout birdied to pull within one.

Dunlap pulled his tee shot into the right rough, but recovered with his approach to tap in for par and claim victory with a 72-hole record low winning score of 29 under 259.

He broke the benchmark of 28 under set by US golfer Patrick Reed in 2014.

Dunlap is the youngest amateur to win on the PGA Tour since 1910.

While he will not collect the $1.5 million prize money, he has secured his PGA Tour card for two years.

Last year, Dunlap became the only player other than Tiger Woods to claim both titles of US Junior Amateur and US Amateur.