Kateřina Siniaková (Czech pronunciation: [ˈkatɛr̝ɪna ˈsɪɲakovaː]; born 10 May 1996) is a Czech professional tennis player. She is the world No. 1 in women's doubles and has held the position for 205 weeks (second-most of all time). She has also been ranked as high as world No. 27 in singles by the WTA, achieved in June 2024.
Siniaková is a twelve-time major champion in women's doubles and one-time champion in mixed doubles. She won seven major titles in her longtime partnership with compatriot Barbora Krejčíková, with whom she completed the career Golden Slam. She has won five other women's doubles majors, one with Coco Gauff and four with Taylor Townsend to complete a second career Grand Slam, as well as one mixed doubles major partnering Sem Verbeek. Siniaková became the world No. 1 for the first time in October 2018 and has held the top doubles ranking for a total of 200 weeks, the second-longest total since the inception of the WTA rankings. Siniaková has won 39 doubles titles on the WTA Tour, including a gold medal at the 2020 Tokyo Olympics, the 2021 WTA Finals, and ten WTA 1000 events.
In singles, Siniaková has won six WTA Tour titles. Her best singles major result was at the 2019 French Open, upsetting world No. 1 Naomi Osaka en route to the fourth round; she has reached the third round at seven other major tournaments.
Siniaková was part of the Czech team that won the 2018 Fed Cup and 2026 Billie Jean King Cup. She also has won two Olympic gold medals: in women's doubles at the 2020 Tokyo Olympics with Krejčíková, and in mixed doubles at the 2024 Paris Olympics with Tomáš Macháč.
Siniaková was born to a Czech mother Hana, an accountant, and Russian father Dmitry Siniakov, a former boxer and her coach. Her younger brother Daniel (born 2003) is also a professional tennis player. Since the COVID-19 quarantine at the 2021 Australian Open, Siniaková had been dating fellow Czech tennis player Tomáš Macháč. In July 2024, Siniaková confirmed they broke up.
She was ranked the world No. 2 junior tennis player in December 2012. With fellow Czech Barbora Krejčíková, she won the girls' doubles titles at the French Open, at Wimbledon and the US Open in 2013.
2012–14: First WTA Tour doubles title
She began playing on the ITF Women's Circuit in the Czech Republic in June 2012. There in a doubles competition, she won her first ITF title. She then made big progress in 2013. She started outside top 1000 in both singles and doubles, but finished year inside top 200 in singles and top 300 in doubles. In March 2013, she won her first ITF singles title at the $10k Frauenfeld, defeating Kathinka von Deichmann in the three sets. Two weeks later, Siniaková made her debut on the WTA Tour in the qualifying draw of Miami Open. She passed qualifying defeating Mandy Minella and Alexa Glatch, but then lost a three-set encounter with Garbiñe Muguruza in the first round of the main draw. In November 2013, she reached her first major ITF final at the $75k Sharm El Sheikh event in doubles, but lost alongside Anna Morgina.
At the 2014 Australian Open, she made her major debut, after passing qualifying but then lost to Zarina Diyas in the first round of the main draw. In July 2014, she won her first match on WTA Tour at the İstanbul Cup defeating Julia Glushko in the first round. Nearly after that, she reached her first WTA doubles final at the Silicon Valley Classic alongside Paula Kania, but they lost to Garbiñe Muguruza and Carla Suárez Navarro. She then went one step further, winning her first WTA doubles title at the Tashkent Open, partnering Aleksandra Krunić. Right after that she made her top 100 debut in doubles. In October 2014, she reached singles semifinals of the Premier-level Kremlin Cup but lost her match against Anastasia Pavlyuchenkova. This brought her into the top 100 in singles, and a week later, she won the title at the $50k Open Nantes Atlantique defeating Ons Jabeur. She finished year with another title at the Open de Limoges, alongside Renata Voráčová.
2015–16: Singles and doubles top 50
At the Australian Open, Siniaková had her first singles Grand Slam win, defeating Elena Vesnina in the first round. In the following round, she lost to Irina-Camelia Begu. In March 2015, she won her first WTA 1000 match at the Premier Mandatory-level Indian Wells Open, defeating another Russian player, Evgeniya Rodina. In May 2015, she had good performances, reaching the singles semifinal and taking the doubles title with Belinda Bencic at the Prague Open. However, after a run to the third-round at the French Open alongside Bencic, she reached top 50. In June 2015, she reached the quarterfinal of the Premier-level Birmingham Classic. By the end of the year, she was standing out more in doubles, reaching final of the Tashkent Open and semifinal of the Premier-level Kremlin Cup.
Siniaková started slowly into the 2016 season, but then shone at the French Open, where she reached semifinals in doubles alongside Barbora Krejčíková. Then, at 2016 Wimbledon, she reached her first singles Grand Slam third round, after defeating Pauline Parmentier and 30th seed Caroline Garcia before being defeated by former world No. 2, Agnieszka Radwańska. Things even got better in July 2016, when she reached her first singles WTA final in Båstad, at the Swedish Open. She lost the final to Laura Siegemund. But then she advanced to the doubles quarterfinals of the US Open, alongside Krejčíková. She followed this up with another singles WTA final at the Japan Women's Open in Tokyo, but lost to Christina McHale. In late October, after a first-round loss at the Kremlin Cup, she made her top-50 debut in singles.
2017: Career singles titles, US Open doubles final
Siniaková had a strong start to the 2017 season, winning her first WTA singles title at the Shenzhen Open. Siniaková began the tournament by defeating Peng Shuai in the first round in two sets, followed by a victory over world No. 4, Simona Halep in three sets, claiming her first win over a top-10 player. Her run continued by beating qualifier Nina Stojanović and world No. 9, Johanna Konta, in three sets. In the final, she defeated Alison Riske to take the title. She then struggled with results, not even reaching a quarterfinal until May 2017. However, during that period, she had success in doubles where she reached the final of Indian Wells and the Premier-level Charleston Open alongside Lucie Hradecká. Then in May 2017, she reached the quarterfinal of the Prague Open in singles, as well as the final in doubles. She continued this form, with good results in doubles, reaching the quarterfinals of the Premier Mandatory Madrid Open and Premier 5 Italian Open with Hradecka. She then reached the doubles semifinal of the French Open for the second year in a row, alongside Lucie Hradecká.
However, in singles, things still were not good until Swedish Open, where she reached her second final. A losing finalist in 2016, this time she succeeded in winning the title, after she defeated world No. 6, Caroline Wozniacki, in the final. On her way to the title, she also defeated two top-20 players, Anastasija Sevastova and Caroline Garcia. She then continued struggling with results in singles, but made did make progress in doubles. At the US Open, she reached her first major doubles final. Alongside Lucie Hradecká, she did not drop a singles set on the way to the final, but then they lost to Latisha Chan and Martina Hingis. Later in the year, she reached the quarterfinal of the Premier-Mandatory China Open and semifinal of the Premier-level Kremlin Cup in doubles. As a result of that, she achieved No. 11 ranking in doubles and finished year as world No. 13, while in singles she ended as world No. 49.
2018: Doubles: No. 1 and two major titles
Siniaková started year well, playing at the Shenzhen Open where she reached the finals in both singles and doubles, but lost to Simona Halep in both. Her run to the singles final included a semifinal-win over Maria Sharapova. She played in the doubles final alongside Krejčíková, but they lost to Halep and Irina-Camelia Begu. She then lost to Elina Svitolina in the first-round match at the Australian Open, and in doubles reached the third round with Krejčíková. Siniaková then reached the quarterfinals in singles at the Premier-level St. Petersburg Ladies' Trophy, and then in May, she reached the quarterfinal of the Prague Open and the semifinal of the Nuremberg Cup. During that period, things got better in doubles where she first reached the semifinals of the Premier 5 Qatar Ladies Open and then the final of the Premier Mandatory Miami Open.