Second Test, Gqeberha (day four of five)
South Africa 425-9 dec: Bavuma 179, Jansen 85; Boland 5-81
Australia 3-1: Smith 28; Jansen 5-33
Australia trail by 422 runs
Australia were forced to follow-on for only the third time in the past 38 years after being dismissed for 99 by South Africa on day four of the second Test in Gqeberha.
Left-armer Marco Jansen took a superb 5-33 and Kagiso Rabada and Wiaan Mulder two wickets each as the Proteas roared back into the Test to give them a real shot at leveling the series.
They were 110-6 early on day three, their hopes severely dented, but scrapped to 425-9 after Temba Bavuma's 179 and now take a 326-run first innings lead.
Australia's surrender was stark.
After opener Nic Maddinson was dismissed late on day three, South Africa took the remaining nine wickets inside 40 overs on the fourth day.
Steve Smith was the tourists highest scoring with 28. No other batter passed 14 and the highest partnership was just 23.
The last time Australia were forced to follow-on was against India at Sydney in 2019. Before that, the most recent previous occasion was the fourth Ashes Test at Trent Bridge in 2005.
It was also the biggest first-innings deficit they conceded since a Test against West Indies in November 1984.
How Australia's collapse unfolded
Jansen sparked the collapse by nicking off nightwatchman Scott Boland with his first ball of the day at the start of the second over.
Four overs later he pinned Travis Head lbw on review for 14 and Marnus Labuschagne was brilliantly caught at slip by Simon Harmer off the bowling of Anrich Nortje for the same score.
Nortje was only able to bowl 3.3 overs because of an apparent groin issue, which will impact the remainder of the Test if he is unable to bowl again.
After Jansen nicked off Matt Renshaw and Alex Carey in the same over, he also found the edge of Beau Webster for his fifth Test five-wicket haul.
Mitchell Starc and Australia captain Pat Cummins followed within 11 balls of Mulder bowling Smith, who had been given treatment to his neck throughout his 88 balls, and, after a brief conversation with his bowlers, captain Bavuma signaled to Australia's dressing room that they would have to bat again.
South Africa now have more than 150 overs to complete victory.