A run to the last four in New York, bookended by crushing routs of long-time foe Maria Sharapova and China's Wang Qiang, brought up a century of US Open wins for Williams, chasing her first Slam crown since the 2017 Australian Open.
Williams, who turns 38 later this month, holds a 4-1 career advantage over Svitolina, but the Ukrainian triumphed in their most recent encounter -- a third-round clash at the Olympics in Rio.
"That was a tough Olympics for me. Oh, man. Lost in doubles for the first time. Just really devastated about that doubles loss. Then obviously singles shortly after," Williams recalled after her 6-1, 6-0 quarter-final demolition of Wang in just 44 minutes.
Williams, who is seeking a 24th major title to match Margaret Court's all-time record, will likely face a far tougher proposition in fifth seed Svitolina.
The 24-year-old Odessa native has yet to drop a set at Flushing Meadows while taking out two-time former champion Venus Williams and 2017 runner-up Madison Keys.
"She is obviously a fighter. She gets a lot of balls back. She doesn't make a lot of mistakes. She's one of those players that does everything really well. So I have to do everything well, too," Williams said.
Svitolina retains fond memories of her 6-4, 6-3 victory over defending Olympic champion Williams in Brazil, a watershed moment which came scarcely two months after she was throttled 6-1, 6-1 by the American at Roland Garros.
"It was unbelievable atmosphere. I played actually a great match. I was very young. Not very young, but I was kind of young at the time. I didn't have big wins at that time. For me, it gave me lots of confidence," Svitolina said.
"It gave me the confidence to actually let me believe that I can play consistent against the top players."
- Singapore boost -
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Svitolina has backed up her Wimbledon semi-final showing in July, where she lost to eventual champion Simona Halep, with another deep run at Flushing Meadows.
She is attempting to become just the second Ukrainian to play in a Grand Slam singles final -- after Andrei Medvedev, who lost in five sets to Andre Agassi at the 1999 French Open.
Svitolina cites last year's WTA Finals title in Singapore as a key factor behind her breakthrough Slam performances this season.
"I think I'm generally stronger. Mentally I'm handling the pressure points better. Sometimes it's possible that you're not there on that day, not playing your best. But you try to find your own path, your own way how to handle those kind of moments," she said.
Williams blasted 25 winners in her rout of Wang, who failed to hit a single one, and Svitolina is fully aware of what to expect from an opponent hunting a seventh US Open title.
"I have to react quickly and try to take my chances when I have them," Svitolina said.
"I think I have to run a lot, like all other matches. That's normal. And try to react -- I played some big hitters in this tournament, a lot, and I have to just react quickly with my feet and with my shots, as well. Then when I have the opportunity, go for it."