Jan Kumstát

Jan Kumstát (born 2 January 2007) is a Czech tennis player. He has a career-high ATP singles ranking of No. 186 and a doubles ranking of No. 450, both in August 2026.

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.

He made his Junior Grand Slam 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 the quarterfinals in boys' singles, but 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.

Kumstát also had good results on the ITF junior circuit, maintaining a 76–40 singles win-loss record and reached an ITF junior combined ranking of world No. 3 on 6 January 2025.

Professional career 2025: Pro beginnings Playing on Pro Tour 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.

2026: Three successive Challenger titles, top 200 In August, he won his second ATP Challenger title at the 2026 Hamburg Ladies & Gents Cup, following his triumph on home soil in Liberec, earlier in the month. As a result he reached the top 250, raising 100 positions in the ATP singles rankings on 24 August 2026. He won his third Challenger title in a row as a teenager, the third to accomplish the feat after Guillermo Coria and Grigor Dimitrov, at home at the 2026 Sekyra Group Prague Open by Advantage Cars and reached the top 200 on 24 August 2026.

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.

ATP Challenger Tour finals

Singles: 3 (3 titles) LegendATP Challenger (3–0)Finals by surfaceClay (3–0)

ITF World Tennis Tour finals

Singles: 3 (3 runner-ups) LegendITF WTT (0–3)Finals by surfaceHard (0–1)Clay (0–2)

Doubles: 4 (2 titles, 2 runner-ups) LegendITF WTT (2–2)Finals by surfaceHard (2–0)Clay (0–2)

Junior Grand Slam finals

Singles: 1 (runner-up)

Doubles: 2 (1 title, 1 runner-up)