Serena Williams is one win away from a record 23rd Grand Slam title after setting up an all-Williams final at the Australian Open. The only person standing in her way is her older sister, Venus.

Second-ranked Serena, a six-time Aussie Open champion, overwhelmed Mirjana Lucic-Baroni 6-2, 6-1 in just 50 minutes in the second women's semifinal on Thursday after Venus Williams beat fellow American Coco Vandeweghe 6-7 (3), 6-2, 6-3.

"She's my toughest opponent - nobody has ever beaten me as much as Venus has," Serena said. "I just feel like no matter what happens, we've won.

"She's been through a lot, I've been through a lot. To see her do so well it's great. I look forward to it. A Williams is going to win this tournament."

Venus, 36, is back in a Grand Slam final for the first time since the 2009 Wimbledon and her first Down Under since 2003, when she lost the only previous all-Williams final at Melbourne Park.

She tossed her racket after clinching the two-hour, 26-minute semifinal on her fourth match point and put her hands up to her face, seemingly in disbelief, before crossing her arms over her heart.

Smiling broadly, she then stylishly pirouetted as she received a standing ovation.

Venus has overcome an energy-sapping illness and is playing her best tennis since being diagnosed with Sjogren's syndrome in 2011.

"Everyone has their moment in the sun," said Venus.

"Maybe mine has gone on a while. I'd like to keep that going. I've got nothing else to do so let's keep it going."

Serena's celebration was more subdued after her one-sided win over 34-year-old Lucic-Baroni, who was playing her first semifinal at a major since Wimbledon in 1999.

Croatian Lucic-Baroni took a selfie with her cell phone on the court before leaving Rod Laver Arena.

Serena didn't get to watch much of her sister's match, but she knew the result before she went out to play.

"Obviously I was really proud of Venus - a total inspiration, my big sister," Serena said.

"She's basically my world and my life. She means everything to me. I was so happy for her. For us both to be in the final is the biggest dream come true for us."

Venus has won seven major titles, but none since Wimbledon in 2008.

Her gap between major finals is the longest for any player in the Open era. She's also lost six of the eight Grand Slam finals she's played against her younger sister, and is 11-16 in career meetings.

Venus is the oldest player to reach a women's major final since Martina Navratilova, then 37 and 258 days, at Wimbledon in 1994.

The 25-year-old Vandeweghe was playing in the last four at a major for the first time and was the only semifinalist younger than 34.

She had advanced with back-to-back wins over top-ranked Angelique Kerber and French Open champion Garbine Muguruza, and took charge against Venus in the first-set tiebreaker.

However, Venus rallied after dropping a set for the first time in the tournament, breaking Vandeweghe four times over the final two sets and putting pressure back on her fellow American.

Earlier in the tournament, Vandeweghe spoke of her admiration for the Williams sisters when she was an up-and-coming player, and once asked for Venus' autograph.

Venus said one of the best things about her longevity in the game was having an influence on other players.

"Growing up, all I wanted was to have an opportunity to play these tournaments. But then you get here and then you have an opportunity to inspire other people," she said. "It's more than a cherry on top. It's more than I dreamed of."

Earlier, Bob and Mike Bryan earned a shot at a seventh Australian Open doubles title after a rain-interrupted 7-6 (7-1), 6-3 semifinal win over Pablo Carreno Busta and Guillermo Garcia-Lopez.

In the final, they'll meet Australian John Peers and Finland's Henri Kontinen.

Venus Williams shows her elation after beating fellow American Coco Vandeweghe in the Australian Open semifinals in Melbourne on Thursday to become the oldest player to reach a women's major final in the Open era.Edgar Su / Reuters