The selectors retained the 14 who were picked for the first two Tests, both of which South Africa lost, and will pick from 16 players.
Both Amla and Steyn have played in three Tests. Amla is the leading run-scorer in South Africa's domestic first-class competition, while Steyn is regarded as the fastest bowler in South Africa and has shown good recent form at domestic level.
The selectors also named a Rest of South Africa team to play the touring New Zealand team in Benoni from April 7 to 10. The New Zealanders arrive on April 5 for a three-Test series.
South Africa v Australia, Johannesburg, March 31 to April 4
South Africa (from): Graeme Smith (captain), Hashim Amla, Mark Boucher, Nicky Boje, AB de Villiers, Boeta Dippenaar, Herschelle Gibbs, Andrew Hall, Jacques Kallis, Garnett Kruger, Andre Nel, Makhaya Ntini, Shaun Pollock, Ashwell Prince, Jacques Rudolph, Dale Steyn.
Rest of South Africa v New Zealand, Benoni, April 7 to 10
Rest of South Africa: Neil McKenzie (captain), Boeta Dippenaar, Alviro Petersen, Davey Jacobs, J-P Duminy, Justin Ontong, Thami Tsolekile, Johan van der Wath, Robin Peterson, Garnett Kruger, Mondi Zondeki, Rory Kleinveldt (12th man).