First-five Handre Pollard scored 31 points as the Springboks thumped Argentina 46-13 in Salta to win the Rugby Championship title.
Pollard scored two tries and kicked five penalties and three conversions to help the Springboks claim their first major trophy for 10 years.
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Earlier on Saturday, world champions New Zealand lost 47-26 to championship runners-up Australia in Perth.
Argentina winger Santiago Cordero shocked the South Africans by going over in the corner in the second minute in Salta but hooker Mbongeni Mbonambi put the visitors 8-7 ahead after 13 minutes after a driving maul.
Pollard and Puma first-five Nicolas Sanchez then got locked into a kicking duel, exchanging penalties, before the 25-year-old South African dived over the try-line just before the break to make it 24-13.
The Springboks' progress slowed early in the second half when scrumhalf Faf de Klerk was sin-binned, only for Pollard to cross again.
Wingers Makazole Mapimpi and Cheslin Kolbe added further tries in the 64th and 67th minute to complete the rout.
The competition has been shortened to one round of matches due to the Rugby World Cup in Japan which starts on September 20.
South Africa last won the Rugby Championship, then known as the Tri Nations, in 2009.
Argentina became the fourth team to join the championship in 2012.
New Zealand had won the past three championships and six of the previous seven.
Join us at 7:30pm Saturday for live updates of the second Bledisloe test between New Zealand and Australia