A total of 18 nations will compete for the trophy, with players from both the ATP and WTA taking part in teams. The list includes some of the biggest names in the game, with the United Cup serving as a warm-up for the Australian Open for many - the first Grand Slam event of the year.
Men’s world No2 Rafael Nadal and No4 Stefanos Tsitsipas are both set to feature, while from the women’s rankings, world No1 Iga Swiatek will take part for Poland and No3 Jessica Pegula will be in place for Team USA.
A total prize pool of US$15million (£12.5m) is on offer, equally split between ATP and WTA players. The individuals will earn different amounts based on participation, team wins and prize money. Ranking points are also on offer, making the United Cup an important early-season event on the season calendar.
Here’s everything you need to know about the newest tournament in tennis.
What is the United Cup?
The United Cup is a mixed team competition which will feature 18 nations playing across three cities, this year Perth, Brisbane and Sydney. The former has indoor hard courts, while Brisbane and Sydney are outdoor hard courts. The same balls will be used as are provided for the Australian Open.
When is it played?
The tournament starts on Thursday 29 December and runs through to 3 January in the group stage, with the City Finals on 4 January, the semi-finals on 6 and 7 January and the first-ever United Cup Final itself on Sunday 8 January.
What is the format?
Each of the three cities will host two groups, making six in total. There are three nations in each group.
In the group stage, there are two ATP and two WTA singles matches, plus one mixed doubles match between each nation. If the overall scores are 2-2 after the singles fixtures, the mixed doubles result decides the winner.
After the round robin, the two nations which top each group in each city will progress to the City Finals.
Then, the three winners of those fixtures - so one from each of Sydney, Perth and Brisbane - will go through to the Final Four, along with the City Finals loser with the best record from their three matches. The Final Four will of course feature semi-finals and then the final, which will be played at the Sydney Olympic Park Tennis Centre.
Are Great Britain taking part?
Yes! The British team are in Group D along with hosts Australia and Spain.
The players involved are (from ATP) Cameron Norrie, Dan Evans, Jan Choinski, Jonny O’Mara and (from WTA) Harriet Dart, Katie Swan, Ranah Stoiber and Ella McDonald.
Team GB’s first fixture is against Australia on 29 December, with Norrie against Alex de Minaur and Swan facing Zoe Hives. The following day, Dart plays Ajla Tomljanovic while Evans plays Jason Kubler. The mixed doubles participants are yet to be decided.
Great Britain play Spain across 31 December and 1 January, with the highlight match being Norrie against Nadal.
Which teams and players are taking part?
Greece: (ATP) S Tsitsipas, M Pervolarakis, S Sakellardidis, P Tsitsipas. (WTA) M Sakkari, D Papamichail, V Grammatikopoulou, S Sakellaridi.
Belgium: (ATP) D Goffin, Z Bergs, K Coppejans, M Geerts. (WTA) E Mertens, A Van Uytvanck, M Kempen, K Flipkens.
Bulgaria: (ATP) G Dimitrov, D Kuzmanov, A Andreev, A Lazarov. (WTA) V Tomova, I Shinikova, G Topalova.
Poland: (ATP) H Hurkacz, D Michalski, K Zuk, L Kubot. (WTA) I Swiatek, M Linette, W Falkowska, A Rosolska.
Switzerland: (ATP) S Wawrinka, M-A Huesler, D Stricker, A Ritschard. (WTA) B Bencic, J Teichmann, Y In-Albon, J Zuger.
Kazakhstan: (ATP) A Bublik, T Skatov, D Yevseyev, G Lomakin. (WTA) Y Putintseva, Z Kulambaveva, G Ainitdinova.
USA: (ATP) T Fritz, F Tiafoe, D Kudla, H Reese. (WTA) J Pegula, M Keys, A Parks, D Krawczyk.
Germany: (ATP) A Zverev, O Otte, D Altmaier, F Fallert. (WTA) L Siegemund, J Niemeier, A-L Friedsam, J Lohoff.
Czech Republic: (ATP) J Lehecka, T Machac, D Svrcina. (WTA) P Kvitova, M Bouzkova, J Maleckova.
Spain: (ATP) R Nadal, P Carreno Busta, A Ramos-Vinolas, D Vega Hernandez. (WTA) P Badosa, N Parrizas Diaz, J Bouzas Maneiro.
Australia: (ATP) A De Minaur, J Kubler, J Peers. (WTA) A Tomljanovic, Z Hives, M Inglis, S Stosur.
Great Britain: (ATP) C Norrie, D Evans, J Choinski, J O’Mara. (WTA) H Dart, K Swan, R Stoiber, E McDonald.
Italy: (ATP) M Berrettini, L Musetti, A Vavassori, M Bortolotti. (WTA) M Trevisan, L Bronzetti, C Rosatello.
Brazil: (ATP) T Monteiro, F Meligeni Alves, M Pucinelli de Almeida, R Matos. (WTA) B Haddad Maia, L Pigossi, C Alves, L Stefani.
Norway: (ATP) C Ruud, V Durasovic, A Petrovic. (WTA) U Eikeri, M Helgo, L Haseth.
France: (ATP) A Rinderknech, A Mannarino, M Guinard, E Roger-Vasselin. (WTA) C Garcia, A Cornet, L Jeanjean, J Ponchet.
Croatia: (ATP) B Coric, B Gojo, M Pecotic. (WTA) P Martic, D Vekic, T Wurth, P Marcinko.
Argentina: (ATP) F Cerundolo, F Coria, T M Etcheverry. (WTA) N Podoroska, M Carle, P Ormaechea.