Ireland produced the shock result of the World Cup so far by beating Tri-Nations champions Australia in Saturday's Pool C clash at Eden Park.
Jonathan Sexton and Ronan O'Gara kicked two penalties each and Sexton also landed a drop-goal for Ireland.
Two James O'Connor penalties were all Australia could manage and they were left without even a losing bonus point.
Ireland almost snatched a late try but Tommy Bowe was caught just short of the line after a surging break from deep.
Replacement scrum-half Conor Murray did get over but the whistle had gone for an offside offence.
The Irish are now top of Pool C with one foot in the quarter-finals.
It was a fantastic forward display by the Irish and to deny Australia a score in the second half was a tremendous effort.
The Aussies were minus influential flanker David Pocock and hooker Steven Moore and the outstanding Irish front-five went on to completely dominate the scrum.
Even though the sides were tied 6-6 at the interval, Australia were still fancied to go on and get their anticipated victory.
But Ireland grew in confidence and secured their first World Cup win over the Wallabies.
Ireland, criticised after an uninspiring opening win over the USA, produced an encouraging first-half display.
Australia did nudge into a 3-0 lead with O'Connor, who had earlier missed, kicking over a penalty after a collapsed Irish scrum.
Sexton sent a penalty side for Ireland but was more successful in the 16th minute to level at 3-3.
The score sparked a good period for the Irish with their fired-up pack making inroads before Sexton landed a drop-goal to nudge his side 6-3 ahead.
O'Connor kicked Australia back on terms at 6-6 and both fly-halves missed further attempts before the break.
Despite the encouraging scoreline, the Irish must have been wary about an Australian backlash in the second half.
Six days earlier the Wallabies had been 6-6 with Italy at the same stage before scoring four tries in 17 second-half minutes to secure a 32-6 victory.
However, Australia were forced on the back foot as Declan Kidney's gutsy Irish summoned a mighty effort.
Sexton landed a 49th-minute penalty to restore the underdogs' lead.
The Leinster fly-half struck an upright with another attempt but O'Gara, on for injured centre Gordon D'Arcy, assumed the kicking duties and slotted over two penalties to put Ireland on course for the upset at 15-6 in the 71st minute.
Australia: Beale, O'Connor, A. Faingaa, McCabe, Ashley-Cooper, Cooper, Genia, Kepu, Polota-Nau, Vickerman, Horwill, Elsom, McCalman, Alexander, Samo.
Replacements: Mitchell for A. Faingaa (75), Slipper for Alexander (63), Higginbotham for Samo (73).
Not Used: S. Faingaa, Simmons, Palu, Burgess.
Ireland: Kearney, Bowe, O'Driscoll, D'Arcy, Earls, Sexton, Reddan, Healy, Best, Ross, O'Callaghan, O'Connell, Ferris, O'Brien, Heaslip.
Replacements: Trimble for O'Driscoll (60), O'Gara for D'Arcy (50), Murray for Reddan (58), Court for Ross (76).
Not Used: Cronin, Ryan, Leamy.
Ref: Bryce Lawrence (New Zealand).