Wozniacki, the 2010 champion, required 80 minutes to eliminate a resurgent Stephens 6-2, 6-3 and reach her sixth final of 2017.
Fifth seeded Svitolina quashed defending champ Simona Halep’s quest for back-to-back titles with a 6-1, 6-1 demolition. The win came just hours after she ousted reigning Wimbledon champion Garbine Muguruza 4-6, 6-4, 6-3 in a quarter-final that was postponed from Friday due to rain.
Stephens, who is ranked 934 in the world, was playing in just her third tournament after missing 11 months while recovering from foot surgery. She beat Petra Kvitova, Angelique Kerber and Lucie Safarova to reach the semi-finals.
Wozniacki’s road to the final included a victory over world number one Karolina Pliskova.
None of Wozniacki’s 25 career titles have occurred this year. She is 0-5 in finals in 2017.
“I had one year where I went to six finals and I won all of them,” Wozniacki said. “I guess it’s a give and take sometimes and just that I keep myself in these situations is awesome. I give myself a chance to win and that’s what I’m going to go out (Sunday) and try to do.”
The Danish sixth seed jumped out to a 3-0 lead in the first set then broke Stephens again to take a commanding 5-1 lead.
After breezing through the first set, Wozniacki let a 3-1 lead in the second slip away as Stephens levelled at 3-3.
Wozniacki regained the momentum and after a brief rain delay she served out the match at 5-3.
In earlier quarter-final matches on Saturday, Halep defeated Frenchwoman Caroline Garcia 6-4, 6-2 while Svitolina rallied from a first set loss to beat Muguruza.
The pair took to the court early Saturday morning after Friday’s rain delays forced the quarter-finals to stretch into a second day.
Halep needed 70 minutes to advance as she didn’t drop a serve and broke Garcia three times.
Svitolina looked the fresher of the two in the semi-final against Halep. She hopes that her conditioning holds up in the title match.
“Of course I’m a little bit tired,” Svitolina said. “I didn’t expect this type of day but I’m very happy that I could stay very focused. Yeah, I’m very happy.”
Saturday’s lopsided win helps avenge a crushing defeat Svitolina suffered at the hands of Halep just two months ago during the French Open.
Svitolina was one game away from sweeping Halep in the quarter-finals before an epic collapse that saw her eventually lose 3-6, 7-6 (8/6), 6-0.