Katerina Siniakova pulled off an incredible comeback at the Jiangxi Open to win her fifth career singles title, saving three championship points before outlasting her fellow Czech Marie Bouzkova 1-6, 7-6(5), 7-6(4) in Sunday's final.

The 3-hour and 33-minute thriller is the first final this season to go more than three hours in length, and it is the sixth longest match of the year overall.

Photo galleries: Winning from match point down in 2023 | All of 2023's three-hour matches

"It was a really tough and big battle," Siniakova said in press after her win. "I’m really excited and proud I kept fighting until the end.

"It’s really tough, and sad that just one can win because both of us just left everything out there."

Siniakova battled back from a break down in both the second and third sets before winning her second singles title of the year. Siniakova won the Bad Homburg title on grass in June, and she was also a finalist at Hong Kong just last week.

Classic between countrywomen: Sunday's championship match was the first all-Czech final since Barbora Krejcikova defeated Tereza Martincova to take the title in the Czech capital of Prague in the summer of 2021.

The latest all-Czech final proved to be a grueling affair before World No.60 Siniakova squeaked past 29th-ranked Bouzkova. Siniakova has now won both of their career meetings, having also beaten Bouzkova in the first round of 2021 Roland Garros.

However, the lengthy match is still not the longest recorded final in WTA history. That record is held by the 1990 Virginia Slims Championships, where Monica Seles beat Gabriela Sabatini -- in five sets -- to take the title at the year-end finals after 3 hours and 47 minutes.

Match moments: No.3 seed Bouzkova hit few errors and used her stellar defense to romp to a 6-1, 4-2 lead on Sunday. However, Siniakova began to match Bouzkova in rally tolerance -- including in a lung-busting 83-second rally won by Bouzkova at 4-3 -- as she started to pull herself back into contention.

Siniakova saved a championship point on her serve at 5-3 in the second set, and she eventually edged ahead 6-5, where she held four set points. However, it was Bouzkova's turn to rebound, erasing all of those set points in a protracted game and lining up a second-set tiebreak.

In the breaker, Siniakova regularly found the corners of the court as she moved ahead 6-2, garnering four more set points. Siniakova needed each and every one before Bouzkova fired a forehand long on Siniakova's eighth set point. The second set alone took 1 hour and 40 minutes.

Despite squandering a 3-1, 40-0 lead in the third set, Bouzkova went up another break at 5-3, where she held two more championship points. However, Siniakova once again rallied her way back into the match, winning three games in a row to serve for the title at 6-5.

Video: Two gripping rallies end Siniakova's win

Bouzkova broke serve to force a decisive final-set tiebreak, but Siniakova came back from 2-0 down to grasp her first championship point with a down-the-line winner for 6-4. There, a Siniakova backhand clipped the netcord before falling over to end the marathon.

Double delight for Siegemund and Zvonareva: Earlier on Sunday, No.2 seeds Laura Siegemund and Vera Zvonareva claimed the Jiangxi Open doubles title with a 6-4, 6-2 victory over No.4 seeds Eri Hozumi and Makoto Ninomiya.

Siegemund and Zvonareva also secured the eighth and final doubles spot at the season-ending GNP Seguros WTA Finals in Cancun by prevailing in the 1-hour and 38-minute final. The duo has won three titles together this year.

It is the 13th career doubles title for 35-year-old Siegemund, and the 15th career doubles title for 39-year-old Zvonareva. The veterans teamed up for the first time at the 2020 US Open, where they took the title. Siegemund and Zvonareva also paired up to reach this year's US Open final.