Venus Williams and Serena Williams celebrate after winning the women’s doubles championship at Wimbledon in 2016. They’re competing against each other Saturday at the Australian Open finals. (Gerry Penny/European Pressphoto Agency)

For the first time in eight years, Venus and Serena Williams will battle against each other in the finals of a Grand Slam, one of the most important tournaments in tennis.

The sisters reached the Australian Open finals after Venus Williams beat fellow American CoCo Vandeweghe in three sets and Serena Williams overwhelmed Mirjana Lucic-Baroni in the semis.

Venus Williams, 36, is the oldest player to reach an Australian Open women’s final in the modern era — and the oldest player to reach the finals of any major since Martina Navratilova at Wimbledon in 1994.

Her sister, who is just one year younger, is trying for an Open-era record 23rd Grand Slam title. Venus has won seven Grand Slam titles of our own.

“I felt like it was in my hands to force this Williams final,” Serena said after beating Lucic-Baroni. “I was feeling a little pressure about that, but it felt really good to get that win.”

On the men’s side of the tournament, 35-year-old Roger Federer punched his ticket to the finals after beating Stan Wawrinka in five sets. Federer is the oldest man to reach a Grand Slam final since Ken Rosewall made the 1974 U.S. Open final at 39. He will play Sunday against the winner of Friday’s semifinal between Rafael Nadal and Grigor Dimitrov.

The Williams sisters play Saturday in Melbourne at 3:30 a.m. Eastern time. It’s the first time they’ve played in an Australian Open final together since 2003, when Serena won what Venus has described as a “battle royal.” It was the first of Serena’s six Australian titles.

Venus hasn’t returned to the Australian final since then and hasn’t reached a Grand Slam final since losing the 2009 Wimbledon title to Serena.

“Everyone has their moment in the sun,” Venus said. “Maybe mine has gone on a while. I’d like to keep that going.”

Given her years-long struggles to overcome an energy-sapping illness called Sjogren’s (pronounced SHOW-grins) syndrome, a jubilant Venus could barely contain her emotions after clinching the semifinal on her fourth match point.

She put her hands to her face, her jaw dropped and she crossed her arms over her heart. A stylish pirouette and wave had the crowd on its feet in support.

Serena’s celebration was simpler — a raised arm after a warm embrace with the 34-year-old Lucic-Baroni, who was playing her first semifinal at a major since Wimbledon in 1999.

“Obviously I was really proud of Venus,” Serena said. “She’s basically my world and my life. I was so happy for her. For us both to be in the final is the biggest dream come true for us.”

Venus has lost six of her eight Grand Slam finals against Serena, and is 11 wins-16 losses overall in career meetings with her sister. She said she would take a winning attitude into the final and had nothing to lose against Serena.

“When I’m playing on the court with her, I think I’m playing, like, the best competitor in the game,” Venus said. “I don’t think I’m chump change either, you know. I can compete against any odds. No matter what.”

The younger Williams sister acknowledged Venus as her 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 … a Williams is going to win this tournament.”