Four of the Hologic WTA Tour's Top 6 will open their 2025 seasons at the United Cup, a nation-based competition that will see stars of the ATP and WTA compete side-by-side across two host cities in Australia.

World No.2 Iga Swiatek, No.3 Coco Gauff, No.4 Jasmine Paolini and No.6 Elena Rybakina will lead the charge for their countries, ringing in the new season as the Australian swing kicks off and winds its way towards the first Grand Slam of the year at the Australian Open.  

Here's what you need to know about the United Cup:

When is the tournament?

The United Cup is an 18-team, mixed-team competition. The 10-day tournament begins on Dec. 27 and will be played across two cities, Sydney (Sydney Olympic Park Tennis Centre) and Perth (RAC Arena). 

Perth’s RAC Arena will host the first day of the United Cup on Friday, Dec. 27, with the group stage in Sydney beginning on Saturday, Dec. 28. 

Teams in Sydney will play on outdoor hard courts. Perth will feature an indoor hard court. Both venues will use the Dunlop Australian Open balls.

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What is the format?

Each city will host three groups of three countries for a total of nine teams, competing in a round-robin format. Ties are comprised of one men's singles match, one women's singles match and one mixed doubles match.

Singles matches are best-of-three tiebreak sets. Mixed doubles matches are two tiebreak sets with a deciding match tiebreak (10 points) at one set-all.
 
Each group winner in each city will advance to the quarterfinals, with one quarterfinal spot in each city awarded to the best runner-up from that city. 
 
Quarterfinal winners progress to the semifinals and finals, both hosted in Sydney. Teams advancing from Perth will receive a travel day and rest day on Jan. 2 and 3.

The semifinals will be played on Saturday, Jan. 4 and the final will be played on Sunday, Jan. 5.

How have the groups been drawn?

United Cup Draw 2024

The groups were drawn in October. Here's where each of the 18 teams will play:

Perth

Group A: [1] United States, Canada, Croatia
Group C: [3] Greece, Kazakhstan, Spain
Group E: [5] China, Germany, Brazil

Sydney

Group B: [2] Poland, Czech Republic, Norway
Group D: [4] Italy, France, Switzerland
Group F: [6] Great Britain, Australia, Argentina

For a full breakdown of the draw and participants, click here. World No.5 Zheng Qinwen has withdrawn from the event. 

Previous champions

The United States, led by Jessica Pegula and Taylor Fritz, won the inaugural United Cup in 2023. Last year, Germany saved match points in the final to defeat Poland 2-1.

What is the prize money and rankings points on offer?

The total prize money pool for the United Cup is a minimum of $10,250,000, split equally between the ATP and WTA. Individual prize money is based on ranking, match wins and team wins. No points will be awarded for mixed doubles.

A player can earn a maximum of 500 points for the week, depending on their ranking.

Notable storylines

Rybakina rings in the new season: The first match of the Hologic WTA Tour season will be played in Perth on Dec.27 and World No.6 Elena Rybakina will help usher in the tour's next chapter. Rybakina, who added ATP legend Goran Ivanisevic to her coaching team over the off-season, will make her United Cup debut when Kazakhstan opens the competition against Spain. Barring any lineup changes, Rybakina will take on Jessica Bouzas Maneiro.

Swiatek and Muchova set to clash on New Year's Day: World No.2 Iga Swiatek and fan favorite Karolina Muchova will face off on Jan. 1 in Sydney, a rematch of the thrilling 2023 Roland Garros final. All three of their previous matches were decided by a 6-4 third set and it will be the first meeting since 2023. Muchova enjoyed a strong finish to her 2024 season, making the US Open semifinals, Beijing final and Ningbo semifinals. Swiatek is looking to lead Poland to the United Cup title. Poland has made the final four in its two previous appearances, falling just short in the final last year. 

Gauff changes things up: After sweeping the Auckland title in her last two seasons, World No.3 Coco Gauff has opted to shake things up in 2025. The 20-year-old American, who finished her 2024 season with a rousing title run at the WTA Finals Riyadh, will join Taylor Fritz in Perth for her United Cup debut. She'll face Canada's Leylah Fernandez and Croatia's Donna Vekic in group play. 

Italy eyes continued domination: The Azurri finished 2024 by sweeping the titles at the Davis Cup and the Billie Kean King Cup and their depth has them well-positioned to win a third straight team competition. World No.4 Jasmine Paolini will lead the charge alongside Flavio Cobolli. The Italians will be formidable if the tie turns to mixed doubles, where reigning US Open champions Andrea Vavassori and Sara Errani will be waiting.

Bencic returns from maternity leave: Former No.4 Belinda Bencic will play her first tour-level event since returning to competition in October. Bencic, 27, has not played a WTA event since September 2023. She gave birth to her daughter Bella in April 2024. She eased into her return on the ITF Tour this fall before storming her way to the final at the WTA 125 in Angers, France in December.

What else is happening in Week 1?

While the United Cup gets a jump start on the 2025 season, the WTA Tour will also see a flurry of action in Brisbane and Auckland.

World No.1 Aryna Sabalenka and Jessica Pegula lead the strong WTA 500 field at the Brisbane International, which begins on Sunday, Dec. 29. Emma Navarro and Daria Kasatkina round out Brisbane's Top 10. Also in the field are Mirra Andreeva, Jelena Ostapenko and Victoria Azarenka.

At the ASB Classic in Auckland, New Zealand, Madison Keys is set to be the top seed at the WTA 250 event, where former No.1 Naomi Osaka and 2021 US Open champion Emma Raducanu are also set to play.  Main-draw play in Auckland begins Monday, Dec.30.