The Wimbledon champion will face fourth-ranked Ana Ivanovic in the quarterfinals.

Williams, in her first tournament since withdrawing from the season-ending champion at Madrid in November due to illness, lost the 2003 Australian final to sister Serena and hadn't gone beyond the fourth round in the season-opening major since.

"I have come close, then this girl named Williams took my dream away," Venus said of her Australian aspirations.

Defending champion Serena Williams moved into the quarterfinals on Sunday along with top-ranked Justine Henin and fifth-seeded Maria Sharapova, a finalist last year.

Serena Williams will play No. 3 Jelana Jankovic, and Henin will face Sharapova.

Ivanovic had a 6-1, 7-6 (2) victory earlier Monday over Denmark's Caroline Wozniacki and was looking forward to her quarterfinal match.

"Definitely a tough opponent. Last two Grand Slams I lost to her. Exactly the time for some revenge," Ivanovic said. "I think I'm a little bit different player than I was last time I played her."

In the adjacent quarter of the draw, No. 9 Daniela Hantuchova needed four match points before finishing off Maria Kirilenko 1-6, 6-4, 6-4. Hantuchova will play Poland's Agnieszka Radwanska, a 1-6, 7-5, 6-0 winner over No. 14 Nadia Petrova.

With sister Serena shouting encouragement, Williams had her hands full with Domachowska.

Far from being intimidated by Williams' power, Domachowska matched it with her own — she had aces on three of her first five serves — along with a variety of spins.

Williams often found herself on the defensive as Domachowska swung for winners at every opportunity.

Williams' right thigh was strapped, and Domachowska gave it a workout, keeping her constantly sprinting from side to side. Williams had to fight back twice from service breaks in the first set, getting back on serve when Domachowska double-faulted on break point, then took the set when the Polish woman netted a straightforward forehand volley.

Williams got the first break of the second set to pull ahead 5-3. Domachowska fended off a match point before breaking back.

Domachowska set up a second match point for Williams with one error while serving 30-30 in the next game, then netted a forehand to finish it off.

"It's good, it gets me ready for the rounds going forward," Williams said of the close match.

Henin beat Taiwan's Hsieh Su-wei on Sunday and now will put her 32-match winning streak on the line against Sharapova in their first meeting since the season-ending championship final in Madrid.

Sharapova pounded fellow Russian Elena Dementieva 6-2, 6-0, breaking the 11th-ranked player in six of her seven service games, including one at love to finish off the match in 62 minutes.

"Justine's the one to beat," Sharapova said. "She's on a pretty good winning streak, but every match is new.

"The one in Madrid was tough but physically she got me in the end — she was tougher than I was in the end. But I had many chances and I was very close to winning."

Sharapova was seeded No. 1 last year when Henin skipped the season-opening major because she was going through a divorce. The Russian star lost to Serena Williams in a lopsided final.

Serena Williams advanced to the quarterfinals with a 6-3, 6-4 over No. 11 Nicole Vaidisova, while Jankovic beat Australia's Casey Dellacqua 7-6 (3), 6-1.

Henin won the Sydney International title in the leadup to the Australian Open, beating second-ranked Svetlana Kuznetsova in the final, and has added wins over Aiko Nakamura, Olga Poutchkova and No. 25 Francesca Schiavone at Melbourne Park.

Sharapova has not dropped a set in wins over Jelena Tosic Kostanic, former No. 1-ranked Lindsay Davenport, Elena Vesnina and Dementieva.

No. 2 Rafael Nadal also advanced to the quarterfinals in straight sets, including an abbreviated 6-3, 3-0 win in the fourth round when Paul-Henri Mathieu withdrew because of an injured left leg late Sunday.

Nadal's match was over at 10:30 p.m. at Rod Laver Arena on Sunday after he won 11 of 12 points to open the second set.

"I was playing well today, maybe I was playing my best tennis in Australia this year," said Nadal, the three-time French Open champion. "I'm happy to be in the quarterfinals — would have preferred not like this."

The last match the previous night did not start until 11:47 p.m. and Lleyton Hewitt finally beat 2006 runner-up Marcos Baghdatis in five sets at 4:33 a.m on Sunday.

Even Roger Federer was taken to five sets Saturday — the first in six years in the first week of a Grand Slam event — against Serbian Janko Tisparevic.

Top-ranked Federer, chasing his third consecutive Australian title and 13th major, faces his first seeded rival when he takes on No. 13 Tomas Berdych of the Czech Republic later Monday.

James Blake faced Marin Cilic, and Hewitt met No. 3 Novak Djokovic in a night match.

David Nalbandian and Juan Carlos Ferrero stepped back on the same court to begin the Sunday schedule little more than six hours after Hewitt and Baghdatis walked off.