Wales staged a thrilling late comeback to launch their Six Nations campaign with a stunning victory over a crushed Ireland in Dublin.
Leigh Halfpenny's last-gasp penalty sealed a remarkable victory in a see-saw encounter in which the lead changed hands five times.
The visitors led 5-3 after the first of two tries for centre Jonathan Davies, but Rory Best's score gave the Irish a 10-5 interval lead.
Davies's second try put Wales back in front before Tommy Bowe appeared to have given Ireland victory, only for a George North try and Halfpenny's kick to steal it from under their noses.
Wales, exhibiting much of the free-flowing rugby that marked their run to the World Cup semi-finals, appeared to have blown their chance when Halfpenny failed to convert North's try from out on the left touchline with four minutes left.
But the visitors persisted and Ireland flanker Stephen Ferris conceded a penalty 30 metres out, which Halfpenny - who had taken over the kicking duties from Rhys Priestland - drilled between the uprights.
Until that point it appeared the goalkicking failures that cost Wales so dearly at the World Cup would come back to haunt them, with Priestland missing two penalties and a conversion.
But Halfpenny held his nerve to condemn Ireland to their first defeat in the opening game of the Championship for eight years.
Wales made their intent clear early on, full-back Halfpenny eschewing a kick to touch to run from his own line. But Priestland's clearance failed to relieve the pressure and the visitors were swiftly penalised at the breakdown, allowing Sexton to make it 3-0.
There was an impressive collective confidence about the visitors though, and they should have hit back immediately after two minutes of sustained pressure on the Irish line.
A cheeky line-out throw to Bradley Davies saw the lock charge up the left touchline before Wales set up camp on the Irish line. Jamie Roberts, twice, and Mike Phillips were both held up short in the right corner before North escaped down the left, and Ryan Jones crashed over.
But Best and Conor Murray did just enough to stop the former captain grounding the ball, at least to the satisfaction of the television match official (TMO).
Wales got the try their early endeavours deserved, however, in the 14th minute. More quick ruck ball saw Phillips feed Priestland and the fly-half stretched around Tommy Bowe to feed Jonathan Davies, who dotted down in the left corner, after confirmation from the TMO.
Priestland's conversion from the touchline came back off the upright, but he should have extended Wales' lead with a penalty from straight in front of the posts in the 19th minute, only to see it come thumping back off the left upright.
With locks Bradley Davies and Ian Evans and flanker Ryan Jones willing workhorses with their ball-carrying, Wales continued to dominate possession.
Giant debutant wing Alex Cuthbert came off his flank to good effect, Jones indulged himself with a cheeky grubber kick down the right touchline, and Priestland spotted space for a cross-kick, but Sexton arrived just ahead of the onrushing North.
Ireland, struggling to make any advances themselves, managed to disrupt Wales whenever they went to the middle of their line-out, picking off three Welsh throws inside the first half-hour.
The hosts gained what appeared a rather soft penalty, Phillips adjudged to have impeded his Ospreys team-mate Bowe on the touchline, when the scrum-half's momentum seemed to make the contact accidental. But Sexton failed to take advantage, pushing his penalty attempt wide.
Ireland finally built up a head of steam as half-time approached and got their reward, quick hands from Murray, Gordon D'Arcy and Fergus McFadden, and an incisive thrust from Bowe, putting hooker Best over for a popular try, Sexton adding the conversion for a 10-5 lead.
Wales returned after the interval without injured captain Sam Warburton, who picked up a dead leg and was replaced by Justin Tipuric, while James Hook entered the fray at full-back with Halfpenny switching to the right wing for the departed Cuthbert.
Sexton's second penalty on the resumption made it 13-5, before Priestland - whose kicking from hand also became ragged - missed another attempt from wide out, his third miss of the afternoon.
That was the cue for Halfpenny to take over the duties, slotting the next attempt after Sean O'Brien was penalised on the deck.
Wales, suddenly revived, were back in the lead two minutes later with a stunning score. A tap-down from Tipuric at the tail of a line-out saw North launched off his left wing, evading two tacklers before a wonderful offload out of the back of his hand sent Davies haring in for his second try. Halfpenny added the extras from in front to put Wales 15-13 ahead.
But back came the hosts, a series of thundering drives forcing Wales to fall offside on their own 22, with Sexton nailing the kick to make it a one-point game going into the final quarter.
The dynamics of a hitherto even contest were altered with 15 minutes left though when Bradley Davies was sin-binned for a tip tackle on Donnacha Ryan, bringing back unpleasant memories for Welsh supporters after the events of the World Cup semi-final when captain Warburton was red carded.
The visitors immediately compounded the setback by losing their own line-out ball inside the 22, and Ireland - led by the charging Paul O'Connell - went for the kill. Wales scrambled desperately in defence, but when play was switched right, Sexton and Kearney exploited the extra space to put Bowe over in the right corner.
Sexton failed to convert from wide out though, and was also off target with a penalty attempt from inside his own half to keep Welsh hopes alive.
Four minutes from time they grabbed the reprieve after kicking a penalty to touch, Roberts and Jonathan Davies combining to send North charging through Bowe and D'Arcy for the try in the left corner.
Halfpenny, faced with half the Irish team charging up at him, pushed the conversion wide of the right upright.
But moments later Stephen Ferris was also adjudged guilty of a tip tackle, on Ian Evans, and yellow carded and Halfpenny made no mistake from in front of the posts to spark wild Welsh celebrations.
Ireland: R Kearney; Bowe, McFadden, D'Arcy, Trimble; Sexton, Murray; Healy, Best, Ross, O'Callaghan, O'Connell, Ferris, O'Brien, Heaslip.
Replacements: O'Gara for Sexton (74), Reddan for Murray (77), Ryan for O'Callaghan (63).
Not Used: Cronin, Court, O'Mahony, D Kearney.
Sin-bin: Ferris (80)
Wales: Halfpenny; Cuthbert, J Davies, Roberts, North; Priestland, Phillips, Gill, Bennett, A Jones, B Davies, Evans, R Jones, Warburton, Faletau.
Replacements: Hook for Cuthbert (41), James for A Jones (70), Tipuric for Warburton (41).
Not Used: Owens, Powell, L Williams, S Williams.
Sin Bin: B Davies (65).
Ref: Wayne Barnes (RFU).