Wales are celebrating a third Grand Slam in 11 years after they put Ireland to the sword in ruthless fashion to storm to the Six Nations title.
After Hadleigh Parkes early try, Gareth Anscombe added a conversion and three penalties for a 16-0 half-lead as Irelands indiscipline cost them dear.
And the fly-half added three more in an equally one-sided second period, Ireland looking nothing like the second-ranked team in world rugby, Jordan Larmours late try no sort of consolation.
Seldom in this championship have Wales been spectacular in attack but their defence has been remorseless and their fortitude under pressure remarkable, and the celebrations will go long into a sodden Cardiff night.
It means Warren Gatland, in his 50th and final Six Nations match in charge, becomes the first coach in Five or Six Nations history to win three Slams, his teams record-breaking winning run now stretching to 14 games.
Cardiff council are expecting up to 275,000 people in the capital, and football fans will also be passing through the city for Swanseas 5.20pm FA Cup clash with Manchester City.
Wales 25 Ireland 7: Gatland given a Grand Slam send-off
For Ireland the tournament ended as it began, with a chastening defeat that leaves significant questions hanging over their World Cup ambitions.
In an atmosphere of feverish excitement Wales exploded from the blocks, bundling Jacob Stockdale into touch from the kick-off and setting up a driving maul from the line-out before Anscombes cute chip was gathered by Parkes for the centre to tumble over the line.
It took a last-ditch tackle in the left-hand corner from Parkes to stop Stockdale striking back immediately after Johnny Sextons cross-kick, although Wales then lost George North to injury, Anscombe moving to full-back, Dan Biggar coming in at fly-half and Liam Williams switching to the right wing.
Ireland were being starved of possession and territory, shipping too many soft penalties, Anscombe landing one from way out wide for 10-0 with 20 minutes gone.
As the rain swept in Joe Schmidts men finally built a period of pressure but struggled to convert it into points.
First Sexton kicked a penalty to the corner but the subsequent driving maul was disrupted by formidable Welsh defence, and another prime attacking opportunity was tossed away when CJ Stander tried to take a quick tap and go from a scrum free-kick 10 metres out and instead kicked it straight into a team-mate.
Anscombe drilled over a second penalty of his own from 40 metres and added another with the clock red to make it 16-0 at the interval, the capacity crowd in full cry, the Slam in their sights.
Ireland needed to score first in the second period but Cian Healy entered a ruck from the side and Anscombe made no mistake from the tee, Irelands woes summed up by Sexton putting the re-start dead.
When Ireland did threaten the Welsh line through a series of powerful drives from their forwards, the ball was thrown into touch by Sexton when it finally went wide.
So comfortable and one-sided was it that the victory songs were ringing round the three tiers of the steep-sided stadium with half an hour still to play.
The tension that so many had expected was totally absent, an Ireland team who had beaten world champions New Zealand in the autumn and won a Slam of their own at Twickenham a year ago utterly unrecognisable.
Anscombes sixth penalty added salt to the wounds as the rain became torrential, the only question whether the visitors would be kept scoreless.
Superlative defence on the Welsh line kept them at bay until replacement Larmours try deep into the final moments, but nothing could dampen the mood as the final whistle sounded.
Wales captain Alun Wyn Jones, speaking to BBC One: “Anything can happen when you work hard and youre a proud nation and weve shown that.
“Warrens the man at the top and weve been under pressure but hes always been unwavering. Hes got a bit left on his contract but Im sure well miss him when hes eventually gone.
“At times weve been unconvincing so we like to think theres still potential in us. Were well aware weve just put a big target on our backs before the World Cup.”
Wales coach Warren Gatland, speaking to BBC One: “It was a fantastic performance, we didnt look too tired did we?
“We spoke beforehand about the players playing for themselves, their families and the fans and being able to create a bit of history. You can never take that away from them now.
“I said if we won the first game against France weve got a good chance of winning the whole thing. If that creates that bit of belief in the players then maybe something like this can happen.”
Ireland captain Rory Best, speaking to BBC One: “Wales had a cracking start. They built into the game. Theyre a very determined side and hard to beat here.
“We couldnt get a footing in the game. Our set-piece wasnt up to the standard that we expect. They put a lot of pressure on us and we struggled to respond.
“Its been a very competitive Six Nations. We have to go and address why we lost. Weve been inconsistent this championship and well have to dust ourselves off and finish the calendar year strong.
“We can talk about the aftermath of this later on but you have to give credit to Wales – theyre deserved Grand Slam winners.”
Wales: L Williams; North, J Davies, Parkes, Adams; Anscombe, G Davies; Evans, Owens, Francis, Beard, Jones (capt), Navidi, Tipuric, Moriarty.
Replacements: Dee for Owens (60), Smith for Evans (53), Lewis for Francis (53), Ball for Beard (70), Wainwright for Moriarty (70), A Davies for G Davies (56), Biggar for North (8), Watkin for Parkes (70).
Ireland: Kearney; Earls, Ringrose, Aki, Stockdale; Sexton, Murray; Healy, Best (capt), Furlong, Beirne, Ryan, OMahony, OBrien, Stander.
Replacements: Scannell for Best (64), Kilcoyne for Healy (58), Porter for Furlong (64), Roux for Beirne (58), Conan for OBrien (51), Marmion for Murray (70), Carty for Sexton (72), Larmour for Kearney (64).