Wales (10) 22
- Tries: Shane Williams, Phillips, J Davies
- Cons: Priestland 2
- Pen: Priestland
Ireland (3) 10
- Try: Earls
- Con: O'Gara
- Pen: O'Gara
Shane Williams celebrates Wales' opening try
Wales crushed Ireland's dream and reached the World Cup semi-finals for the first time since 1987 with an impressive display in Wellington.
Wing Shane Williams squeezed over for Wales' early opener, Keith Earls responding in kind after the break.
But in-form scrum-half Mike Phillips' clever dive and centre Jonathan Davies' burst past prop Cian Healey settled the contest in Wales' favour.
Rhys Priestland added seven Welsh points to Ronan O'Gara's five.
Wales, led by outstanding flanker Sam Warburton, held off the challenge of an Ireland side that topped Pool C to book a semi-final meeting with either England or France.
Lock Luke Charteris epitomised the Welsh effort, making 16 tackles before being replaced by Bradley Davies at the break.
Whenever Ireland threatened, Wales seemed to have enough numbers and commitment to cope, other than when wing Earls made the most of his chance.
The Welsh line-out also stood up to the notable challenge of Paul O'Connell and Donncha O'Callaghan, while at the scrum Ireland were unable to repeat the effort that led to victory over Australia.
Jamie Roberts was again the focus of Welsh efforts with ball-in-hand and, with Priestland guiding their play and Phillips continuing a rich vein of form, Warren Gatland's side proved superior in midfield to the O'Gara-Brian O'Driscoll axis on which Ireland have relied in the past decade.
Wing Williams extended his Welsh record try tally to 56 in the third minute as the Pool D runners-up began with an assurance that belied the occasion.
They patiently built a multi-phase attack in which Roberts took a high ball going forward before Halfpenny put Williams over in the right corner.
Video referee Giulio de Santis confirmed the score and Priestland converted from the wide angle.
Indiscipline and Ireland's ability to build pressure denied Wales the chance to capitalise on their good start.
In quick succession Faletau went over the top at a ruck, George North failed to roll away from a tackle and Dan Lydiate was caught offside at a breakdown but, instead of kicking for goal, the Irish settled for a series of attacking line-outs.
When Roberts eventually managed to put Wales on the front foot, O'Driscoll intercepted Phillips' pass to launch Ireland's best attack of the opening half, in which Gordon D'Arcy's dummy and run underlined the threat posed by Declan Kidney's side.
However, Shane Williams somehow managed to hold Sean O'Brien off the floor as the flanker crossed the line to deny Ireland a first try.
An O'Gara penalty finally got the Irish on the board after the Welsh again fell foul of the tackle laws but Halfpenny's long-range penalty restored Wales' seven-point advantage by the interval.
Ireland returned rejuvenated for the second period and drew level shortly after the restart when Stephen Ferris and Tommy Bowe combined to give Earls the time and space to cross at the corner, with O'Gara adding the conversion.
The scores were tied for only five minutes as Phillips stole away on the blindside after Alun Wyn Jones' drive to give Wales an advantage they would not surrender.
Priestland failed with the conversion and also saw a penalty rebound off the post, but Wales went further ahead when centre Davies made the most of Healey's appearance in the midfield defence to fend off the prop and burst clear to score.
The time, Priestland was able to add the conversion to put Wales 12 points ahead with 15 minutes remaining.
Ireland's attempt a response saw replacement scrum-half Eoin Reddan conjure a superb pass to O'Brien.
But the Irish flanker was halted three metres short and knocked on before Healey was penalised at the scrum, allowing Wales to clear.
Ireland threw all they had left at Wales in the closing stages, but the defence coached by Shaun Edwards proved equal to the task.
Leigh Halfpenny (Cardiff Blues); George North (Scarlets), Jonathan Davies (Scarlets), Jamie Roberts (Cardiff Blues), Shane Williams (Ospreys); Rhys Priestland (Scarlets), Mike Phillips (Bayonne); Gethin Jenkins (Cardiff Blues), Huw Bennett (Ospreys), Adam Jones (Ospreys), Luke Charteris (Dragons), Alun Wyn Jones (Ospreys), Dan Lydiate (Dragons) Sam Warburton (Cardiff Blues, capt), Toby Faletau (Dragons).
Lloyd Burns (Dragons), Paul James (Ospreys), Bradley Davies (Cardiff Blues, for Charteris, 40), Ryan Jones (Ospreys), Lloyd Williams (Cardiff Blues), James Hook (Perpignan, for Priestland, 77), Scott Williams (Scarlets).
Rob Kearney (Leinster); Tommy Bowe (Ospreys), Brian O'Driscoll (Leinster, capt), Gordon D'Arcy (Leinster), Keith Earls (Munster); Ronan O'Gara (Munster), Conor Murray (Munster); Cian Healy (Leinster), Rory Best (Ulster), Mike Ross (Leinster), Donncha O'Callaghan (Munster), Paul O'Connell (Munster), Stephen Ferris (Ulster), Sean O'Brien (Leinster), Jamie Heaslip (Leinster).
Sean Cronin (Leinster), Tom Court (Ulster), Donncha Ryan (Munster, for Heaslip, 74), Denis Leamy (Munster, for Ferris, 74), Eoin Reddan (Leinster), Jonathan Sexton (Leinster), Andrew Trimble (Ulster, for Earls, 71).
Craig Joubert (South Africa).
Wayne Barnes (England), Romain Poite (France)
TMO: Giulio de Santis