Australia will play New Zealand in the World Cup final after they held off an inspired Argentina fightback to win another thriller of a semi-final. A three-try first-half blitz, including two from Adam Ashley-Cooper, helped the Wallabies into a 13-point lead.
Argentina refused to yield and Nicolas Sanchez's flawless boot - he kicked five penalties in all - saw them trail by seven points with 26 minutes to go. But Ashley-Cooper completed a hat-trick of tries late on to secure victory.
Roared on by a passionate support that included football World Cup winner Diego Maradona, Argentina had chances in the second half as they took control up front and utilised their explosive runners.
But they lacked the composure to exploit several possible overlaps and Australia will now face neighbours New Zealand in the final. The two great Antipodean rivals have never met before in a World Cup final, and a tournament that has been blessed with so many epic contests may yet have one more.
Pocock the difference?
Argentina may feel they did not get the rub of Wayne Barnes' refereeing, particularly in losing Tomas Lavanini to a questionable yellow card and seeing both Will Genia and Tevita Kuridrani escape censure for more obvious offences.
Yet they will also rue their own lack of ruthlessness compared to their opponents, too often losing possession deep in enemy territory when the momentum and crowd were with them.
Number eight David Pocock was once again outstanding for Australia as his side won countless turnovers, fly-half Bernard Foley's nine points from the tee also critical in deflating the Puma charge.
David Pocock made 13 carries - the most in the Australia side.
Wallabies start with a bang.
Barely a minute had gone before the Wallabies struck, lock Rob Simmons picking off Sanchez's obvious inside-pass to race under the posts.
Sanchez landed a simple penalty but when scrum-half Martin Landajo knocked on taking a quick tap deep in his own 22 Australia cashed in again, Israel Folau's dummy run creating space for Foley's long mis-pass the other way to send Ashley-Cooper sprinting into the right-hand corner.
Foley's second conversion made it 14-3, and with Pocock a relentless burglar at the breakdown, Argentina were in trouble despite Sanchez's second penalty.
Worse was to come when young second row Lavanini was controversially yellow-carded for tackling Folau without using his arms. This time it was Matt Giteau's perfectly timed mis-pass which set Ashley-Cooper way into the left-hand corner after a series of barrelling drives and quick ball from the forwards sucked in the defence.
The Pumas would not be cowed. Sanchez's third penalty narrowed the deficit to 10 points and just before half-time only a bungled off-load from Juan Martin Hernandez after Santiago Cordero's fizzing break denied supporting full-back Joaquin Tuculet a certain try.
Rob Simmons scored his first try of the World Cup - and it was the fastest at the 2015 tournament.
Argentina fight back but fall short
Sanchez landed two penalties and Foley one in a frantic period after the break as Argentina - three key men down after injuries to captain Agustin Creevy, winger Juan Imhoff and Hernandez - twice closed to within a converted try.
The Pumas began to win the scrum battles and with it the territory but three times they had clear overlaps out wide and, unlike the Wallabies, could not convert.
Australia centre Kuridrani was lucky to stay out of the sin-bin after deliberately kicking the ball away, with scrum-half Genia equally fortunate after tackling his man off a penalty without having dropped back 10 metres.
And Ashley-Cooper made the Pumas pay when Drew Mitchell produced a scything run in and out of the blue-and-white shirted rearguard before throwing out a pass that the winger gathered off the turf to complete his hat-trick.
Man of the match
Pocock has arguably been the player of the tournament for his phenomenal breakdown work, but in becoming only the second man after Jonah Lomu to score three tries in a World Cup semi-final, Ashley-Cooper will be the toast of his bleary-eyed and sleep-deprived homeland.
Adam Ashley-Cooper is only the second player to score a hat-trick in a RWC semi.
Argentina: Tuculet; Cordero, Bosch, J Hernandez, Imhoff; Sanchez, Landajo; Ayerza, Creevy, Herrera; Petti Pagadizabal, Lavanini; Matera, Fernandez Lobbe, Senatore.
Replacements: Amorosino for Imhoff (19) De la Fuente for J Hernandez (44), Cubelli for Landajo (56), Figallo for Herrera (61), Alemanno for Petti Pagadizabal (58), Noguera for Matera (64), Isa for Senatore (49). Not Used: Montoya. Sin Bin: Lavanini (26).
Australia: Folau; Ashley-Cooper, Kuridrani, Giteau, Mitchell; Foley, Genia; Slipper, Moore, Kepu; Douglas, Simmons; Fardy, Hooper, Pocock.
Replacements: Toomua for Folau (64), Beale for Giteau (47), Phipps for Genia (67), Smith for Slipper (53), Polota-Nau for Moore (60), Holmes for Kepu (53), Mumm for Simmons (67), McCalman for Fardy (56).