Poland will face Italy in their first ever Billie Jean King Cup semi-finals after beating the Czech Republic 2-1 in a hard-fought tie that ended in the early hours of Sunday.
Czech Marie Bouzkova won the opener against Magdalena Frech 6-1, 4-6, 6-4, and it was up to Swiatek to keep Poland's chances alive to reach the tournament's semi-finals for the first time.
The world number two, undefeated in Billie Jean King Cup in the last five years, did just that but was well tested by teenager Linda Noskova, whom she beat 7-6(4), 4-6, 7-5 in a tight encounter that lasted two hours and 39 minutes.
Swiatek broke to take a 3-1 lead in the final set before Noskova, who knocked her out of the Australian Open in January, broke back and pulled level at 4-4.
The Pole took the match to even the tie 1-1 before returning on court with Katarzyna Kawa for the decider against doubles world number one Katerina Siniakova and Bouzkova.
Swiatek and Kawa then sealed a stunning 6-1, 6-4 victory over the Czechs in one hour and 11 minutes.
"I'm so happy to play with Iga and that we made it. I mean, it's really great day, the start of the great day," Kawa said as she began her 31st birthday celebrations on Sunday.
The five-time Grand Slam winner Swiatek added: "In 20 minutes I'll be dead! It was an exhausting day, but everything worked. We did a great job, we won."
ITALY EDGE JAPAN
Italy became the first nation through to the last four after they beat Japan 2-1 with a deciding straight sets doubles victory by Jasmine Paolini and Sara Errani over Shuko Aoyama and Eri Hozumi earlier on Saturday.
The tie was locked at 1-1 after French Open and Wimbledon runner-up Paolini beat 56th-ranked Moyuka Uchijima 6-3 6-4 in the second singles match to put the Italians on the board.
While the opening set of that match was all one-way traffic, the second was level at 4-4 before world number four Paolini pulled away with the win in little over one hour.
Paolini returned for the doubles with Errani, who has five doubles Grand Slam titles to her name. The pair, who won gold at the Paris Olympics, dominated to beat the Japanese duo 6-3, 6-4.
After Japan were 5-1 down in the second set, Aoyama and Hozumi showed great spirit to make it 5-4 but their resistance was short-lived as the Italians sealed the win.
"The strategy was to serve well and try to be aggressive because the game was really fast. They played amazing in doubles, so it was a really stressful match. But in the end, I'm grateful that we did it as a team," Paolini said after their doubles win.
"This year I'm a little bit used to it," the 28-year-old added when asked about playing singles and doubles back-to-back. "But I will rest now, I will work with the physios here."
Earlier, American-born Japanese player Ena Shibahara, ranked 135th in the world, battled back from a set down to beat 54th-ranked Elisabetta Cocciaretto 3-6, 6-4, 6-4.
Four-times Billie Jean King Cup champions Italy, who were runners-up to Canada in 2023, last won the title in 2013.
Canada will face Great Britain and Australia will play Slovakia on Sunday for spots in the other semi-final.
