Venus Williams posted another triumph for the old guard at the Australian Open by beating Anastasia Pavlyuchenkova to reach her 21st grand slam semi-final.

Williams, at 36, is the oldest singles player in the women's draw at Melbourne Park but she rolled back the years on Rod Laver Arena to beat 24th seed Pavlyuchenkova 6-4 7-6 (7/3).

The victory puts Williams into the last four here for the first time in 14 years and continues a late resurgence for the American, who has now made the semis twice in her last three grand slams.

She is the oldest woman to get to this far at the Australian Open since the start of the Open era.

Williams' progress also adds another chapter to something of a fairytale tournament for the game's senior stars, after Roger Federer and Rafael Nadal, 35 and 30 respectively, both made the quarter-finals of the men's draw.

The lesser-known Mirjana Lucic-Baroni, 34, is also into the last eight at a grand slam for the time since Wimbledon in 1999.

Williams will now play Coco Vandeweghe, who beat seventh seed Garbine Muguruza, in an all-American semi-final.

"I'm so excited," Williams said. "Today was such a hard-fought match, she never let up. We've always had these quality matches and I knew today would be nothing less.

"It's wonderful to be here to start the year out - I want to go further, I'm not happy with this, but I'm so happy to be in a position to go further."

Coco Vandeweghe blasted her way into her first grand slam semi-final with a dominant display of power tennis to destroy French Open champion Garbine Muguruza 6-4 6-0.

The 25-year-old American, who was equally as impressive in dispatching world number one Angelique Kerber in the previous round, controlled the match from the seventh game when she achieved her first break of serve.

Having taken 56 minutes to wrap up the first set, Vandeweghe raced through the second to clinch the match and her semi-final place 27 minutes later.

"It's amazing to be in a semi-final. But, you know, not satisfying. I want to keep going, keep playing," Vandeweghe told reporters. "There's more things to do out on a tennis court that I'm hoping to achieve."

Vandeweghe, whose previous best grand slam tournament was making the quarter-finals at Wimbledon in 2015, will now meet Williams.