Muchova and Sabalenka had never progressed beyond the third round in Paris.
Svitolina was booed by some sections of the crowd because she snubbed the Australian Open champion after the final point, instead of shaking her hand at the net.
Sabalenka walked up to the net, and leaned on the top of it with both hands, looking at Svitolina as she walked. Svitolina did not look in her direction and went straight to the sideline.
"It just was an instinct, like I always do after all my matches," Sabalenka explained in her first news conference since her second-round win. She had said she was skipping open news conferences for her own "mental health and well-being."
Sabalenka is from Belarus, and Svitolina -- playing in her first major since becoming a mother -- is from Ukraine. Belarus aided Russia in its invasion of Ukraine in February 2022, and the war continues. Like other players from Ukraine, including Sabalenka's first-round opponent last week, Svitolina has not been shaking hands with players from Belarus or Russia after matches.
When asked whether Sabalenka's actions "inflamed the situation," Svitolina said, "Yeah, I think so, unfortunately."
Sabalenka's all-risk tennis paid dividends despite 37 unforced errors. Her aggressive returns and deep groundstrokes put Svitolina on the backfoot from the start. Under pressure at the beginning of the second set and 2-0 down, Sabalenka raised her game to win four games in a row and sealed the match with a forehand winner.
Sabalenka has yet to drop a set in the tournament.
Pavlyuchenkova played for more than three hours in her previous match and appeared tired as she got off a sluggish start and gave away too many easy points.
She tried to fight back using her powerful groundstrokes, but her hopes of a comeback were dashed when she went down 4-1 in the second set after another big forehand bounced wide.
Pavlyuchenkova missed most of the 2022 season with a knee injury. Ranked No. 333, she was the lowest-ranked woman to reach the Roland Garros quarterfinals in the Open era, and the lowest at any Grand Slam since 2017.
Muchova has also been slowed by injuries as an abdominal problem forced her to rest for six months after the 2021 US Open. She damaged an ankle during her third-round match at Roland Garros last year.
Muchova will be playing her second semifinal at a major after making it that far at the Australian Open two years ago.
The Associated Press and ESPN's D'Arcy Maine contributed to this report.