World Cup - Welsh down Ireland to reach semis
The game was level at 10-10 with 30 minutes remaining but Mike Phillips scored an opportunistic try before Jonathan Davies made the game safe with a third Welsh try.
Shane Williams had opening the scoring after just two minutes as Wales led 10-3 at half-time but Keith Earls' score had levelled the game up shortly after the break.
Wales made a spectacular start as a superb take of a high ball by Jamie Roberts started an attack that saw record Welsh try scorer Williams cross in the right corner.
Rhys Priestland added a great conversion from the touchline to make it 7-0 early on.
Ireland had large amounts of territory in the opening period and were twice held up just short of the line with captain Brian O'Driscoll eschewing simple penalty attempts in favour of lineouts inside five metres.
Ronan O'Gara did get his side on the scoreboard with a simple penalty after 23 minutes but Leigh Halfpenny restored Wales' seven point advantage four minutes later with a long-range kick.
The tackle count in the first-half was Wales 89 Ireland 55 to underline how much ball Declan Kidney's side had and they made that possession count early in the second-half.
A pass from Conor Murray was not exactly where he intended but great hands from Stephen Ferris kept the move alive and winger Earls crashed over in the corner and was awarded the try after consultation with the TMO official.
O'Gara nailed the conversion from the touchline to level the scores but there would be no fairytale finish for captain O'Driscoll and his golden generation.
Ireland were on level terms for just six minutes before sublime work from scrum-half Phillips who darted around the Ireland cover defence down the blindside before diving over in the corner.
Priestland missed the conversion and saw two penalties hit the post but that did not prove costly as Davies scored to ensure Wales won back to back matches against Ireland for the first time since 1988.
Wales were dominating the breakdown and outside centre Davies found the gap between Cian Healy and Earls, taking advantage of some slack defending to burst over the line and on this evidence Sam Warbuton's side will fancy their chances of reaching a maiden World Cup final.
2' Williams try - Wales 5-0
3' Priestland conversion - Wales 7-0
23' O'Gara penalty - Wales 7-3
27' Halfpenny penalty - Wales 10-3
44' Earls try - Wales 10-8
45' O'Gara conversion - 10-10
50' Phillips try - Wales 15-10
63' Davies try - Wales 20-10
64' Priestland conversion - Wales 22-10