Venus Williams has returned to the quarter-finals for the ninth time at the Australian Open, where she reached the same round on debut in 1998.

The 36-year-old, seven-time major winner had a 6-3, 7-5 fourth-round win on Sunday over No181-ranked Mona Barthel, who won three matches in qualifying and then beat two Australian wild cards and Olympic gold medallist Monica Puig in the first three rounds.

Williams has advanced without dropping a set, finding her rhythm quickly after pulling out of a tournament in Auckland and withdrawing from the doubles before the first round at the Australian Open because of an elbow problem.

"It was just not ideal to start the year like this, and it was a ton of anxiety, to be honest," Williams said of her preparation. "But really, at the end of the day, it's about walking to the net, shaking hands as the winner.

"This is where you want to be... but this is not the end-all for me. This is not the end goal."

Williams will next play No24-seeded Anastasia Pavlyuchenkova, who beat No8 Svetlana Kuznetsova 6-3, 6-3 in the opening match of Day Seven at Rod Laver Arena.

Pavlyuchenkova's win over fellow Russian Kuznetsova left Williams as the only Grand Slam winner left in that quarter of the draw.

Williams has a 3-2 edge in career meetings with Pavlyuchenkova, including wins in the last two matches.

But she hasn't advanced beyond the quarter-final round at Melbourne Park since her loss to younger sister, Serena, in the 2003 final. Against Barthel, she won 90 percent of points when she got her first serve into play, hit 31 winners and fired four aces while not serving any double-faults.

Barthel was the lowest-ranked player to reach the fourth round of the women's draw here since 2010, although she has a career-high ranking of 23 and was consistently top 50 before an illness last year caused her slide down the rankings.

"I know what it's like to be down on my luck," Williams said. "We've played a couple of tough matches before. Today I expected to have some competition."