Australia's Cameron Smith has described his stunning victory in the 150th Open Championship at St Andrews as "unbelievable". 

"To win an Open Championship in itself is probably going to be a golfer's highlight in their career. To do it around St Andrews, I think is just unbelievable," said the 28-year-old.

"This place is so cool. I love the golf course. I love the town," added Smith, who finished the tournament on 20-under-par at the Old Course.

Smith turned in a virtuoso putting display on the back nine to spoil what many had expected to be a Rory McIlroy party, overhauling a four-shot deficit with a closing 64 that included five birdies in a row from Holes 10 to 14.

The afflable Auatralian saved par from 10 feet at the notorious 'Raod Hole', the par-four 17th, and finished off with a close-range birdie on the final green to claim his maiden Major title.

54-hole co-leader McIlroy closed with 70 to settle for third on 18-under-par, one shot behind American Cameron Young who stole runner-up honours with a closing eagle after successfully driving the last green.

Smith becomes the fifth Australian to claim the Claret Jug, joining Peter Thomson (1954-56, 1958, 1965), Kel Nagle (1960), Greg Norman (1986, 1993) and Ian Baker-Finch (1991).

Told that Nagle's 1960 win came in the 100th edition at St Andrews, Smith quipped: "Hopefully we can keep that trend going with the win every 50 years! That would be nice, wouldn't it?

"I think just in general, all the names on there, every player that's been at the top of their game has won this championship. Yeah, it's pretty cool to be on there. It really hasn't sunk in yet. I don't think it will for a few weeks," he said.

Smith paid tribute to the Australian fans for their vocal support. "To the fans. I had a lot of support out there, especially the Aussie guys who really kept me going out there. This one’s for Oz. Thanks guys!"

54-hole co-leader Victor Hovland of Norway was never in the mix, closing with a 74 to tie for fourth on 14-under-par with England's Tommy Fleetwood.

Best Asian honours went to Thailand's Sadom Kaewkanjana, who turned in a superb closing 65 to finish T11 on 11-under-par.