Andy Murray will face a tough start to his Australian Open campaign against Matteo Berrettini as Novak Djokovic makes his return on Tuesday.
Murray, a five-time finalist at Melbourne Park, will take on Italian 13th seed and last year's semi-finalist Berrettini on Rod Laver Arena.
Serbia's nine-time champion Djokovic returns a year after his controversial deportation saw him miss the Slam.
Women's second seed Ons Jabeur also features in the night session.
Elsewhere, Britain's Dan Evans faces Argentine Facundo Bagnis as he bids to join compatriots Cameron Norrie and Emma Raducanu in the second round.
Former world number one Murray, 35, is currently ranked 66th and his unseeded status leaves him vulnerable to difficult draws at the majors, as evidenced by his difficult opener against 2021 Wimbledon runner-up Berrettini.
But the three-time major winner says he feels healthy and has "no timeframe" on retirement - four years after he feared the 2019 tournament could be the last of his career.
Djokovic, unable to compete at last year's event because of his Covid-19 vaccination status, said the reception he received on his return to the Australian Open in a practice match with Nick Kyrgios last week made him feel "emotional".
The Serb, 35, begins his bid for a record-extending 10th men's title versus Spain's Roberto Carballes Baena, having clinched his 21st Grand Slam title at Wimbledon in July.
Before Djokovic's match, Jabeur - runner-up at Wimbledon and the US Open last year - takes on Slovenian Tamara Zidansek on Rod Laver Arena from 08:00 GMT.
Also in the women's draw, French fourth seed Caroline Garcia plays Canadian qualifier Katherine Sebov and Belarusian fifth seed Aryna Sabalenka faces Czech Tereza Martincova.
Meanwhile, men's second seed Casper Ruud of Norway starts against Czech player Tomas Machac, while fellow top-10 players Andrey Rublev, Taylor Fritz and Holger Rune are also in action and Alexander Zverev makes his major return following injury.