Rafael Nadal headlines the action on Rod Laver Arena as he faces Argentina's Federico Delbonis in the second round of the singles. Alexander Zverev. who's pledged to donate his entire prize money to bushfire relief should he win the tournament, is playing on the same court earlier in the day, against Egor Gerasimov, the world number 98.
Zverev: I'll donate every cent to bushfire relief if I win the Australian Open
Karolina Pliskova, the second seed on the women's side of the draw, has a tough task against Germany's Laura Siegemund.
MATCH OF THE DAY
Don't take your eyes off the first match on Margaret Court Arena - sixth seed Belinda Bencic takes on one-time French Open champion Jelena Ostapenko. The Latvian has had a difficult time of it lately, but crushed Ludmilla Samsonova 6-1, 6-4 in the first round. Meanwhile, the Swiss enjoyed a resurgent 2019, only fading slightly at the last. This should be good.
POTENTIAL UPSET OF THE DAY
Expect America's Lauren Davis to give fifth seed Elina Svitolina more than a little to think about as they headline the day on Margaret Court Arena.
What a day it will be for qualifier Harriet Dart - starting the night session off, on Rod Laver Arena no less, against fourth seed Simona Halep. The 23-year-old had a massive match in the first round last year when she faced 30th seed Maria Sharapova - and was served up a double bagel. She will have learnt plenty from that.
Heather Watson had to wait a long time to play her first-round match, but she's back on court quickly - playing Elise Mertens, the 16th seed, on Court 22.
Elsewhere, 14th seeds Jamie Murray and Neal Skupski get their doubles campaign under way, facing Hubert Hurkacz and Vasek Pospisil. Luke Bambridge partners Ben McLachlan against Mate Pavic and Bruno Soares while Joe Salisbury teams up with Rajeev Ram to play another Brit, Cam Norrie, who pairs with Marton Fucsovics; and Ken Skupski partners Santiago Gonzalez against John Millman and Soonwoo Kwon.
SHOWCOURT SCHEDULE (play starts at midnight UK time)
Rod Laver Arena
Garbine Muguruza (ESP) v Ajla Tomljanovic (AUS)
Laura Siegemund (GER) v Karolina Pliskova (CZE)
Ergo Gerasimov (BLR) v Alexander Zverev (GER) 
Not before 08:00 GMT
[Q] Harriet Dart (GBR) v Simona Halep (ROU) 
Rafael Nadal (ESP)  v Federico Delbonis (ARG)
Margaret Court Arena
Belinda Bencic (SUI)  v Jelena Ostapenko (LAT)
Daniil Medvedev (RUS)  v [Q] Pedro Martinez (ESP)
[WC] Priscilla Hon (AUS) v Angelique Kerber (GER) 
Not before 08:00 GMT
Andreas Seppi (ITA) v Stan Wawrinka (SUI) 
Elina Svitolina (UKR)  v Lauren Davis (USA)
Donna Vekic (CRO)  v Alize Cornet (FRA)
[WC] Jessica Moore (AUS) / Astra Sharma (AUS) v Ashleigh Barty (AUS) / Julia Goerges (GER)