Steyn is this season's leading Super 14 points scorer
South Africa have named two uncapped players in a 28-man squad to face the British and Irish Lions.
Coach Peter de Villiers included fly-half Morne Steyn and full-back Earl Rose for the three-match Test series which runs from 20 June to 4 July.
Rose was part of the Springboks squad that toured Europe at the end of 2008, while fly-half Steyn won the Super 14 title with the Bulls on Saturday.
Veteran captain John Smit will lead the South African side.
The backbone of the squad is supplied by the Bulls and the Sharks, with 10 players from each of the strongest South African Super 14 teams.
Steyn has been a key figure in the Bulls' charge to the Super 14 title and finished as the competition's top points scorer with 191.
De Villiers said: "Morne Steyn earned his spot by performing week in, week out - he had an outstanding Super 14.
"If we can maintain the form shown by the Blue Bulls, even 20% less, then we will be unbeatable."
De Villiers dismissed any concern about a lack of recognised full-backs in the squad. "There are guys in our squad who have played in the position before," he said.
"We have a few options - JP Pietersen has played there, so has Frans Steyn and Earl Rose hasn't done badly in the position. Even Morne Steyn can play there if called upon."
The squad also includes Sharks prop Deon Carstens and Bulls centre Wynand Olivier, both of whom last played for the national team in 2007.
De Villiers added: "There were at least 12 players who could have made the squad, but I think we have the players who can go out and do the job," he said.
"With four Super 14 captains in the side, some of whom have captained South Africa, my job becomes easier all the time."
The Springboks will face the Lions in the first Test in Durban on 20 June, followed by games in Pretoria and Johannesburg on 27 June and 4 July respectively.
An Emerging Springboks side has been named to face the Lions in Cape Town on 23 June, consisting of players who have not yet represented South Africa.
It will be captained by Bulls forward Dewald Potgieter and coached by De Villiers' assistant Dick Muir, assisted by Jerome Paarwater and Stanley Raubenheimer.
South Africa squad:
Backs: J de Villiers (Stormers), F du Preez (Bulls), J Fourie (Lions), B Habana (Bulls), A Jacobs (Sharks), E Januarie (Stormers), O Ndungane (Sharks), J Nokwe (Cheetahs), W Olivier (Bulls), R Pienaar (Sharks), JP Pietersen (Sharks), E Rose (Lions), F Steyn (Sharks), M Steyn (Bulls).
Forwards: J Smit (Sharks), V Matfield (Bulls), A Bekker (Stormers), B Botha (Bulls), S Burger (Stormers), D Carstens (Sharks), B du Plessis (Sharks), R Kankowski (Sharks), T Mtawarira (Sharks), C Ralepelle (Bulls), D Rossouw (Bulls), J Smith (Cheetahs), P Spies (Bulls), G Steenkamp (Bulls).
Emerging Springboks squad:
Backs: H Adams (Bulls), B Basson (Griquas), B Francis (Bulls), Z Kirchner (Bulls), L Ludik (Lions), M Newman (Stormers), E Rose (Lions), D van Rensburg (Leopards), J Vermaak (Lions), L Vulindlu (Sharks).
Forwards: J Botes (Sharks), J Deysel (Sharks), W du Preez (Cheetahs), W Kruger (Bulls), P Cilliers (Sharks), T Liebenberg (Stormers), B Maku (Bulls), D Potgieter (capt, Bulls), W Steenkamp (Bulls), S Sykes (Sharks), F van der Merwe (Lions), D Vermeulen (Stormers).