Son hits winner as South Korea beat Australia to reach Asian Cup semis
It was another great escape for the Koreans, who needed a 96th-minute penalty from Hwang Hee-chan to stay alive after Australia took the lead late in the first half through Craig Goodwin.
It was the fourth time in five games that Jurgen Klinsmann's South Korea had scored in second-half injury time in Qatar.
Tottenham's Son, Asia's best player and South Korea's skipper, had yet to fully make his mark at the tournament but he delivered when it counted.
First, he won a penalty when Lewis Miller brought him down in injury time at the end of normal time, then he stepped up to curl home a sublime free-kick from the edge of the box in the 104th minute.
Klinsmann, who has been under fire for South Korea's performances in Qatar, led his team in a wild celebration at the end.
Australia finished the match with 10 men after Aiden O'Neill was red-carded for lunging at Hwang at the end of the first period of extra time.
The Koreans are looking to win the Asian Cup for the first time since 1964.
They will have to do without Kim Min-jae in the semi-final, after the Bayern Munich defender picked up his second booking of the tournament.
Jordan will be their opponents after they beat Tajikistan 1-0 earlier in the day.
Australia came into the match with two days' extra rest, with South Korea also battling the effects of a gruelling penalty-shootout win over Saudi Arabia in the last 16.
Wolverhampton Wanderers forward Hwang started for the first time in the tournament after returning from a hip injury.
South Korea dominated the first half but it was Australia who opened the scoring in the 42nd minute.
Hwang In-beom gave the ball away in the Korean defence and Connor Metcalfe floated the ball to the back post for Goodwin to volley home.
The Socceroos should have doubled their lead 10 minutes after the restart when Mitchell Duke blazed over, after goalkeeper Jo Hyeon-woo had denied Martin Boyle with a double save.
Duke spurned another opportunity when he headed wide in the 84th minute, and the Koreans made them pay with the equaliser from the spot deep into injury time.
Son then completed the turnaround, curling the ball inside Maty Ryan's post for the winner.
