Stosur had lost all of her four career meetings with Williams, but posted a 6-3, 4-6, 6-3 triumph in the quarterfinals, her second victory of the day.
The match came just 2 hours after Stosur completed a match against Galina Voskoboeva that had been suspended by rain late Thursday. Stosur had a 4-2 lead in the first set when the match was halted and she went on to record a 6-3, 4-6, 6-2 victory.
"I would have preferred not to play two three-set matches, but I'm happy to be through," Stosur said. "It's only one win, but I'm very, very happy to have beaten Venus now. It's always a good challenge coming up against the players you've never beaten."
Stosur prevented what would have been the first matchup in three years between Williams and her sister Serena.
Serena Williams reached the semifinals when Sabine Lisicki was forced to withdraw in the first set with a left ankle injury. Stosur will play the Williams sisters in back-to-back contests.
The other semifinal will send Polona Hercog against Lucie Safarova. Hercog breezed past Nadia Petrova 6-1, 6-2 and Safarova was a surprise 6-3, 6-3 winner over Vera Zvonareva.