Wicketkeeper-batsman Klaasen and allrounder Mulder replace Andile Phehlukwayo and Chris Morris in the 15-man party for the games, the first of which is due to get under way at Kingsmead on March 1
Heinrich Klaasen could play against Australia
The uncapped pair of Heinrich Klaasen and Wiaan Mulder have been named in the South Africa squad for the first two Test matches against Australia.
Wicketkeeper-batsman Klaasen and allrounder Mulder replace Andile Phehlukwayo and Chris Morris in the 15-man party for the games, the first of which is due to get under way at Kingsmead on March 1.
Each could become South Africa's 100th Test player since the country's return to the international cricket arena during the upcoming series.
"Klaasen has been tremendously impressive in the white-ball matches he has played for the Proteas and we firmly believe he can become just as good a player in the five-day format," said selector Linda Zondi.
SOUTH AFRICA SQUADFaf du Plessis, Hashim Amla, Temba Bavuma, Quinton de Kock, Theunis de Bruyn, AB de Villiers, Dean Elgar, Heinrich Klaasen, Keshav Maharaj, Aiden Markram, Morne Morkel, Wiaan Mulder, Lungisani Ngidi, Vernon Philander, Kagiso Rabada
"He has averaged nearly 50 with the bat in Sunfoil four-day cricket this season and hit two centuries.
"We are also keen to have a back-up wicketkeeper to De Kock in the squad.
"The selection of Mulder continues our strategy to expand our pool of allrounders against top quality opposition. He is a batting allrounder and his selection will depend on how we decide to balance our starting XI.
"It has been very exciting this season to see the way young players have settled into the various Proteas squads and done well and this is a continuation of that policy."
Wiaan Mulder has been named in the squad