Jan Kumstát
Jan Kumstát is a Czech tennis player. He has a career-high ATP singles ranking of No. 675 achieved on 2 February 2026 and a doubles ranking of No. 636 achieved on 2 February 2026.
Kumstát won the boys' doubles title at the 2025 Australian Open.
Junior career
In the summer of 2022, Kumstát won gold in the singles at the European Youth Olympic Festival in Banská Bystrica.He was part of the Czech team that won the 2023 Junior Davis Cup.
Kumstát also had good results on the ITF junior circuit, maintaining a 76–40 singles win-loss record. He made his major jr. debut at the 2024 Australian Open. He defeated local opponent Hayden Jones on his way to reaching the final, where he lost to Japanese Rei Sakamoto. He also reached the quarterfinals in the doubles category, with Norwegian Nicolai Budkov Kjær.
Playing with compatriot Jan Klimas, Kumstát was a runner-up in the boys' doubles event at the 2024 Wimbledon Championships. The pair was defeated by Alexander Razeghi and Max Schönhaus in the final.
Kumstát went into the 2025 Australian Open as the highest-ranked junior in the tournament. He reached quarterfinal in the boys' singles, where he lost to Swiss Henry Bernet. Despite that loss, a few days later he reached the doubles final in Melbourne, with American Maxwell Exsted. They were crowned champions of that event, defeating Ognjen Milić and Egor Pleshivtsev in straight sets.
He reached an ITF junior combined ranking of world No. 3 on 6 January 2025.
Professional career
Playing on Pro Tour in 2025 Kumstát reached his first two ITF singles finals at back to back events in Italy and Slovenia. In doubles he played another two finals with fellow Czech players David Poljak and Denis Peták. He also made his ATP Challenger Tour debut in Ostrava defeating Murphy Cassone in the first round.Personal life
Kumstát is from Prostějov, Czechia. He is the son of former ice hockey player Pavel Kumstát and nephew of Petr Kumstát. His mother, Kateřina, was a professional volleyball player.ITF World Tennis Tour finals
Singles: 2 (2 runner-ups)
| Result | W–L | Date | Tournament | Tier | Surface | Opponent | Score | |||||||||||||||
| Loss | 0–1 | M15 Segrate, Italy | WTT | Clay |  dts|Aug 2025Doubles: 4 (2 titles, 2 runner-ups)
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