Wales took advantage of Peter O’Mahony’s 14th-minute red card to beat Ireland in their Six Nations opener.
Flanker O’Mahony became the first Irishman to be sent off in the Six Nations following a reckless elbow to the head of prop Tomas Francis.
Ireland bounced back to lead 13-6 at half-time through a Tadhg Beirne try and Johnny Sexton’s boot.
Tries from George North and Louis Rees-Zammit and 11 points from Leigh Halfpenny sealed success for Wales.
But they nearly lost it at the death, with a penalty giving Billy Burns the chance to kick for the corner and a potential match-winning line-out drive, only for the replacement Ireland fly-half to kick the ball dead, to Wales’ huge relief.
It was a fourth win for Wales coach Wayne Pivac in 11 competitive matches and the first against a leading nation following previous successes against Italy and Georgia.
Ireland are still to win an away game under Andy Farrell despite the 14 men of Ireland enjoying territory and possession advantage while Wales’ forwards dominated the tackle charts.
It was a bruising battle with Wales losing Dan Lydiate, Johnny Williams, Hallam Amos and Tomos Williams to injury.
Ireland lock James Ryan failed a head injury assessment and skipper Sexton’s afternoon ended 11 minutes from time when Wales flanker Justin Tipuric’s knee accidentally caught him in the head.
After playing the autumn series at Parc y Scarlets, Wales returned to their Principality Stadium home after the iconic ground had been used as a coronavirus hospital in 2020. The eerie Cardiff city centre atmosphere belied what the Welsh capital would usually be like on international day.
After a period of experimentation, Pivac returned to some tried-and-tested men by picking the most experienced Wales starting side in history.
Captain Alun Wyn Jones played his first game for two months after recovering from a knee injury and was sporting a black eye following an altercation in training with Jake Ball, who was not named in the squad.
Wales had already been disrupted by suspended duo Liam Williams and Josh Adams, the latter due to a Covid-19 breach.
A cagey start saw Leigh Halfpenny open the scoring before his opposite number Hugo Keenan demonstrated his attacking abilities with an incisive break.
Dan Lydiate’s first international match for more than two years was cut short after his right leg buckled underneath him, forcing the flanker off to be replaced by Josh Navidi.
The game’s controversial moment came in the 14th minute when O’Mahony was red carded for a reckless arm to the head of Francis when trying to clear out a ruck.
Referee Wayne Barnes showed the Munster man a deserved red and it looked as if the game’s complexion would change.
Irish indiscipline continued with a high tackle from Sexton on Johnny Williams, allowing Halfpenny to double the lead.