PARIS -- Sloane Stephens never stood a chance.
The match was so one-sided that the 26th-seeded Konta won all but one point on her serve in the second set -- and the one that she lost was a double fault.
Konta served six aces, stepped into the court to crush winners off second serves and never gave the seventh-seeded Stephens time to find her rhythm or groove.
"To play one of the best players in the world and then play at the level I did, I feel really proud of myself," Konta told the crowd.
The match ended in a brisk 71 minutes, with spectators still filing into their wooden seats inside Court Philippe Chatrier as it was finishing.
"There is not much you can do when someone is playing like that," Stephens said. "I didn't get a chance to really get into the match. ... She executed a good game plan, and that was that."
Vondrousova improved to 26-5 since exiting the Australian Open in the second round -- a stretch that includes finals in Budapest and Istanbul -- and now her first Grand Slam semifinal.
Konta, who beat both Stephens and Vondrousova during her recent run to the Italian Open final, improved to 3-0 in her career against Stephens.
Fans attempted to motivate Stephens with shouts of, "Come on Sloane," and "Just keep working," but the 2017 US Open champion struggled to deal with Konta's pace and highly aggressive shots.
Konta hit 25 winners -- more than twice as many as Stephens did -- and they were evenly distributed between her forehand (nine) and backhand (eight), with a few volleys mixed in, too.
Early in the second set, Stephens was stretched out wide and replied with a desperation forehand that landed on the line. Stephens must have thought her shot was going out, because she stood still and didn't even attempt to run down Konta's reply.
"I don't even remember what that point was," Stephens said.
On Konta's first match point, Stephens hit a forehand that was called in by the line judge. But the chair umpire came down and overruled the call after inspecting the mark on the clay.
Konta has now reached the semifinals in three of the four Grand Slam tournaments after the Australian Open in 2016 and Wimbledon in 2017. She has never progressed to a final at a major.
Vondrousova needed four match points to end a four-match losing streak against Martic and reach the semifinals at Roland Garros.
"It was a very tough match," Vondrousova said. "... I think Roland Garros is my lucky place."
The Associated Press contributed to this report.