Rory McIlroy birdied the 18th as Adam Scott bogeyed to hand the Northern Irishman a dramatic one-shot victory at the Australian Open in Sydney - his first in over a year.

McIlroy began the day four shots behind the Australian but a round of 66 - highlighted by an eagle on the par-five seventh - powered him to victory as Scott faltered.

The overnight leader started and finished with bogeys as he carded a 71, letting slip what would have been his second Australian Open title and the triple crown of Australian golf - the Australian Masters, PGA and Open in the same season - achieved only once before by Robert Allenby in 2005.

Instead, McIlroy can celebrate a first tournament win since the DP World Tour Championship in Dubai last November.

After the third-round tussle between the two failed to ignite, Sunday proved a much better encounter.

McIlroy followed up his eagle with a birdie from close range at the eight to take a share of the lead.

Scott replied with a birdie on the ninth after an outstanding iron shot to regain the advantage, and after matching birdies on the 13th they headed to the final hole with Scott still up by one.

But the Australian put himself in trouble when he missed the green and then over-hit a chip to leave himself with a long putt.

He could only bogey and that left McIlroy with the fairly simple task of rolling it in from five metres for the win.

McIlroy told a press conference: "I stayed patient, I knew anything could happen.

"I always believed I could win, he (Scott) had a couple of chances but was unlucky.

"The support this week was phenomenal, the atmosphere was fantastic."

Of whether he would return next year, McIlroy added: "I've always tried to come back and defend wherever I've won."