They will be hoping to avoid the upsets that have shaken up the first Grand Slam of the year.
Most of the carnage has come in the men's draw, where defending champion Rafael Nadal and second seed Casper Ruud are both out.
Women's second seed Ons Jabeur followed them out of Melbourne Park late on Thursday in round two.
Poland's Swiatek will hope to take full advantage as she pursues a fourth Grand Slam crown - but first in Melbourne.
She will be expected to make light work of 100th-ranked Spaniard Cristina Bucsa.
Also on day five, in-form American Pegula faces Ukraine's 61st-ranked Marta Kostyuk, also on Margaret Court Arena.
On Rod Laver Arena, the 18-year-old Gauff, the seventh seed, goes up against fellow American Bernarda Pera.
Also on centre court will be an intriguing encounter between 24th seed Victoria Azarenka, a two-time Australian Open champion, and 10th-seeded American Madison Keys.
Danielle Collins, who lost last year's final to now-retired Ashleigh Barty, is another American player in action.
She faces a test in 22nd seed Elena Rybakina, last year's Wimbledon champion.
In an unpredictable men's draw, Daniil Medvedev and Stefanos Tsitsipas will look to take full advantage of the depleted field.
Novak Djokovic is the hot favourite to win the title for a record-extending 10th time, but both men can stake their claim on Friday.
Third seed Tsitsipas of Greece, who is yet to win a Grand Slam, plays 63rd-ranked Dutchman Tallon Griekspoor on Rod Laver Arena in the third round.
He has enjoyed strong support from Melbourne's Greek community and says it is like playing at home.
The final match of the day could be the best of all, teeing up Russia's Medvedev against dangerous 29th seed Sebastian Korda of the United States.
Seventh seed Medvedev, a former world number one, is determined to go one better this time.
He has lost the last two finals at Melbourne Park and went down in a five-set thriller to Nadal last year.
