Ireland 21 Australia 19
Ireland outhalf Ronan O'Gara fired a long-range drop goal two minutes into injury-time to complete a dramatic victory over Argentina and claim a clean sweep of Autumn Test scalps.
The boot of Felipe Contepomi and a try from centre Federico Martin Aramburu put Argentina - who led 16-6 at half-time - in command but Ireland chipped away at the tourists' lead after the interval.
O'Gara - who did not miss a single shot at goal in five attempts - did the damage with four second-half penalties and then popped up with the winning drop-goal to snatch victory from the jaws of defeat.
It was a second time in two weeks the Munster star had claimed the man of the match honours - he also accounted for all of Ireland's points during their 17-12 triumph against South Africa.
But it could have been so different had Argentina maintained the momentum they built up in a devastating opening 20 minutes which saw them race 10-0 ahead and left Ireland shell-shocked.
The Triple Crown winners entered the last leg of the November internationals high in confidence following triumphs over the Springboks and the United States, but it nearly fell to pieces at the last hurdle.
When news of Argentina's shock 24-14 success over Grand Slam holders France filtered through last Saturday, Eddie O'Sullivan's men knew they faced possibly the hardest match of the three.
They only had to cast their minds back to any of the previous five meetings with the Pumas - the last a nail-biting 16-15 win during the pool stages of the 2003 World Cup - for further indication of the challenge before them.
And 13 months later it was more of the same as Argentina pushed them to the wire once again, thanks mainly to a magnificent start.
Contepomi kicked three early points and Lansdowne Road then fell into silence as the Pumas' lead was extended in the fifth minute thanks some excellent work from the outhalf's brother, Manuel.
The Newman centre came up with the ball at the breakdown and, with only O'Driscoll in front of him he drew the British and Irish Lions star and fed Federico Martin Aramburu who galloped home.
O'Gara slashed the deficit with a drop-goal but Argentina wasted little time in restoring their 10-point cushion with another Felipe Contepomi penalty and these were worrying times for the Irish, who were camped in their own half.
They managed to break into opposition territory and threatened briefly but the Pumas had slowed the ball down and the moment was gone, forcing O'Gara to attempt a second drop-goal which he stabbed wide despite being in front of the posts.
By the 20th minute Ireland had assumed control of the game and eagerly took the opportunity to exert some pressure of their own.
A hanging crossfield kick from O'Gara set up a lineout after Pumas flanker Martin Durand had caught the ball and been bundled into touch and this created the platform to launch a fresh assault.
Malcolm O'Kelly nearly barged his way over but was eventually knocked backwards in the tackle and then O'Gara tried to wriggle through but Felipe Contepomi flew in with a try-saving tackle.
Argentina briefly wrestled back the initiative - they were causing the Irish pack problems in the scrum - but a powerful run from O'Connor deep into the Pumas' half halted their momentum.
Spreadbury spotted the tourists straying offside and gave O'Gara a shot at goal which he accepted, but soon after Argentina launched a quickfire counter attack which almost saw Ireland concede again.
The Pumas were not done yet though, rumbling forward with purpose and forcing Ireland to infringe out wide which gave Contepomi the opportunity to land another penalty on the stroke of half-time.
The Irish continued to hammer away at Argentina's right touchline with some success after the break, forcing the frustrated South Americans to concede another penalty which O'Gara stroked between the uprights.
But each time Eddie O'Sullivan's men appeared to have clawed their way back into the match Contepomi would pounce, slotting a fourth penalty in the 49th minute to send his side 10 points clear.
A shimmy from O'Driscoll sliced open the Pumas' defence and with 10 metres to go the Leinster midfielder looked destined to cross but Stade Francais full-back Juan Martin Hernandez appeared out of nowhere and made a decisive tackle.
Ireland were winning ball but Argentina's defence gave nothing away and a third O'Gara penalty was all the home team had to show from another foray into the opposition half.
O'Gara was on target with a 67th-minute three-pointer before Pumas number eight Gonzalo Longo was sent to the sin-bin for giving away too many penalties in the 72nd minute.
That left Argentina effectively down to 14 men for the rest of the match and O'Gara rubbed salt into the visitors' wounds by kicking the ensuing penalty.
With a packed Lansdowne Road roaring them on, Ireland surged forward in injury-time, setting the platform for O'Gara to fire the drop-goal which sealed a dramatic victory.
PA