Ireland beat reigning champions Wales 30-22 in a pulsating six-try encounter as they announced their RBS 6 Nations title credentials.
First-half tries by wing Simon Zebo, on his first Six Nations appearance, and prop Cian Healy helped put daylight between the teams before imperious centre Brian O'Driscoll touched down shortly after the break at the Millennium Stadium.
Wales, 30-3 down and facing humiliation, stirred through touchdowns from wing Alex Cuthbert, full-back Leigh Halfpenny and substitute prop Craig Mitchell during a frantic second period when Ireland saw hooker Rory Best and scrum-half Conor Murray sin-binned.
But they ultimately left themselves with far too much to do as Ireland, despite playing almost the entire second period inside their own half, scored 30 points in Cardiff for the first time since 2001.
They condemned Wales to an eighth successive defeat - and a fifth Millennium Stadium reversal on the bounce - with interim head coach Rob Howley still searching for a first win against another Test-playing country.
Wales must now pick themselves up for a trip to Paris next Saturday, where title favourites France await, but yet again they were punished for failing to leave their starting blocks until it was way too late.
Such sluggishness proved a trait of Wales' four-Test autumn campaign this season, and Ireland needed no second invitation to capitalise, deservedly winning despite conceding 19 unanswered points after the 43rd minute.
It was Wales' first Six Nations loss since March 2011, but Ireland, in contrast, now have critical momentum that could drive them all the way to silverware in a tournament they last won four years ago.
Both teams launched their Six Nations campaigns on the back of considerable injury problems.
Wales were without Rhys Priestland, Richard Hibbard, Alun-Wyn Jones, Luke Charteris, Bradley Davies, Dan Lydiate and Ryan Jones, while Ireland arrived in Cardiff minus key men Paul O'Connell, Tommy Bowe and Stephen Ferris.
But the scene was set under an open roof in glorious winter sunshine for a thrilling tussle, especially with so much at stake.
And it was Ireland that struck the opening blow after 11 minutes courtesy of sublime brilliance from O'Driscoll.
His ability to freeze the opposition defence surfaced in all its glory, with three Welsh defenders transfixed as he teased them before delivering a scoring pass to Zebo.
Zebo took the plaudits through scoring a try on his Six Nations debut, but O'Driscoll once again showcased breathtaking ability at the highest level, with Sexton's conversion making it 7-0.
Wales, despite some resilient defensive work from full-back Leigh Halfpenny, could not get out of their own half, and there was worse to come as Ireland smelt blood.
A Sexton penalty after 20 minutes extended the lead, and even when Wales occasionally moved into Irish territory their efforts were undone by a handling error or by choosing the wrong option.
And Ireland did not require a second invitation to make Wales pay, cutting them open again midway through a hopelessly one-sided affair.
Best charged down Wales fly-half Dan Biggar's kick, and after skipper Jamie Heaslip linked slickly in midfield, Zebo's stunning flick off the back of his shin to hand enabled the move to continue.
It then needed a degree of patience from Ireland, but they handled things superbly in the build-up and Healy burrowed over from close range.
Sexton converted and then added another penalty, giving Ireland a 20-point advantage after 29 minutes and effectively sealing victory with indecent haste.
Halfpenny belatedly opened Wales' account with a penalty, but Sexton cancelled that out before the break as Ireland trooped off 23-3 ahead.
Wales had no option but to throw caution to the wind after the break. Ireland, though, had other ideas, and O'Driscoll crossed from close range for his team's third try.
Sexton added the extras, and there was only a hint of consolation for Wales when Cuthbert scored his sixth Test try eight minutes into the second period, with Halfpenny's conversion making it 30-10.
Wales, for the first time, were in territorial control, and they battered away at Ireland's line through a concerted passage of play that ended with Halfpenny touching down wide out after Best was yellow-carded by referee Romain Poite.
Although the visitors still enjoyed a healthy advantage, Wales were a different team from the opening period as they minimised their mistakes and put Ireland under the cosh.
The game was camped inside Ireland's 22, and when Mitchell muscled his way over during the final knockings their remained hope that Wales could somehow still complete a miracle comeback.
But it was not to be, with Ireland claiming a first win against Wales in the last four attempts and setting themselves up for England's Dublin visit on Sunday week.
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