Geoff Ogilvy rocketed into a two-stroke lead by carding a flawless penultimate round at the Australian Open in Sydney, but two-time major champion Jordan Spieth remains hot on his tail.

Ogilvy fired the lowest score of the tournament so far at the Royal Sydney Golf Club as the 2006 U.S. Open champion posted a bogey-free eight-under-par 64 on Saturday.

The eight-time PGA Tour winner holed eight birdies to top the leaderboard at 11 under through 54 holes.

Ogilvy made the most of favourable early morning conditions, going out to an imposing six-under 30 following back-to-back birdies from his opening two holes before adding four in succession starting at the sixth.

The Australian picked up shots at the 16th and 18th holes as he earned the outright lead, ahead of Spieth and Co.

American star Spieth, Aussie Aaron Baddeley and New Zealand's Ryan Fox are tied for second at nine under.

Spieth - last year's runner-up and champion in 2014 - carded a four-under-par 68 to be within touching distance of the lead.

The former world number one's round featured six birdies and two bogeys.

Baddeley shot a third-round 67, while Fox recorded a 71.

Overnight leader James Nitties dropped down into a tie for sixth at seven under following his two-over-par 74.

Adam Scott is also four shots off the pace after his round of 71.