Muchova, a former French Open runner-up, clinched a 7-6(4), 6-4 victory on Court One to set up a semi-final meeting with Coco Gauff.
"It's unbelievable, I'm super happy with today's win, this atmosphere," said Muchova.
"I'd played three times on this court and it had been 0-3.... but I finally made it today and got that win.
"I was nervous, I was very nervous."
Muchova had lost in the first round on each of her past four Wimbledon appearances, but has now bettered her previous best run at the All England Club -- quarter-final defeats in 2019 and 2021.
Osaka had reached the last eight for the first time with a statement victory over world number one Aryna Sabalenka but could not repeat that performance, making 32 unforced errors in a disappointing display.
Wimbledon 2026
Wimbledon is taking place from June 29th to July 12th at the All England Club in south-west London. With 128 players in the draw, it is the third of the four Grand Slams of the tennis season and the only one played on grass.
Men's singles draw and results | Women's singles draw and results | All you need to know about the tournament | Find all our Wimbledon coverage here
