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 just so excited that I have an opportunity to play again." @Venuseswilliams #AusOpen #Venus pic.twitter.com/nlmCO654vQ

— #AusOpen (@AustralianOpen) January 24, 2017

"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."

Williams' run is all the more remarkable given the Australian Open has never been her strongest grand slam.

The seven-time major champion has lost in the third round or earlier in five of her last seven attempts and her prospects took another blow when she retired in Auckland earlier this month through injury.

"It wasn't the easiest start to the year," Williams said. "I had so much anxiety going into this one so to be standing here with an opportunity to go further, it's like, 'Oh my god'."

Williams believes she can go on and win the title.

"I try to believe," Williams said. "Should I look across the net and believe the person across the net deserves it more?

"This mentality is not how champions are made. I'd like to be a champion, in particular this year. The mentality I walk on court with is: I deserve this."

"I have a lot to give, a lot of great tennis left in me."@VenusesWilliams on her longevity and impact on tennis #AusOpen pic.twitter.com/553OiCsonQ

— wta (@WTA) January 24, 2017

Vandeweghe will offer a stern test, however, after powering past Muguruza 6-4 6-0 to reach her first grand slam semi-final.

The 25-year-old, who knocked out top seed Angelique Kerber in the previous round, hit 31 winners and broke Muguruza four times in a ruthless display of baseline hitting.

"I just tried to play my best and stay within myself," Vandeweghe said.

"She finally cracked and then once I got rolling in the second it was like a freight train, you couldn't stop it."

Vandeweghe, 11 years Williams' junior, will face an opponent she used to idolise as a girl and once asked for an autograph.

"It's an honour to play a great champion like Venus and someone I grew up watching," Vandeweghe said.

"I sought after her for an autograph way back when, there was a tournament in La Costa in California.

"I believe she did give it to me but it took two matches to push through the crowd and get one."

Muguruza had never before made it to the last eight in Melbourne and remained philosophical in defeat.

"I think she played unbelievable," the Spaniard said. "I have zero regrets about my performance."