They overtake New Zealand, whose 40-month reign at the top is the longest period any side has continually held the number one position since the rankings began in 2003.
The highest climbers this week are Argentina who jump three places to third thanks to their brilliant 34-10 third-fourth place play-off win over France last Friday. Beaten World Cup finalists England have slipped from third to fourth position.
Meanwhile, the one other change in the top ten sees France drop two places to sixth, with Australia (fifth), Ireland (seventh), Scotland (eighth), Fiji (ninth) and Wales (tenth) completing the list of the world's top-ranked sides.
World Cup matches counted for double in the IRB World Rankings - a team gained 1.5 times the standard amount if they won a match by more than 15 points.
Outside of the top ten, there are bound to be changes in the rankings next weekend as a result of the six European Nations Cup matches taking place.
IRB WORLD RANKINGS (As of October 22) -
(1) South Africa 90.89 rating points
(2) New Zealand 89.63
(3) Argentina 87.56
(4) England 85.61
(5) Australia 84.21
(6) France 80.43
(7) IRELAND 78.66
(8) Scotland 76.83
(9) Fiji 75.82
(10) Wales 74.08