Welsh triumphed 25-7 in a pulsating atmosphere at the Millennium Stadium to clinch its first title since 2013 and first Grand Slam for winning all five matches since 2012.
Center Hadleigh Parkes scored a try after 80 seconds and fly-half Gareth Anscombe kicked 20 points as Wales’ earned a fourth Grand Slam of the Six Nations era and third under Kiwi coach Warren Gatland, who is leaving his post after this autumn’s World Cup.
The win also extended Wales’ record to 14 straight victories in its last competitive encounter before the World Cup.
Going into the final weekend, Wales, Ireland and England all still had a chance to win the title, but the Welsh sealed the championship before England’s match against Scotland later Saturday.
“I’m proud of the players, it’s not about me,” said Gatland, who becomes the first coach in history to win three Grand Slams. “We spoke beforehand about playing for themselves and their families and this crowd and Wales as a whole, and being able to create a bit of history. It was a dazzling performance by us.”
Wales captain Alun Wyn Jones told the BBC: “Anything can happen when you work hard and you’re a proud nation and we’ve shown that.
“Warren’s the man at the top and we’ve been under pressure but he’s always been unwavering. At times we’ve been unconvincing so we like to think there’s still potential in us. We’re well aware we’ve just put a big target on our backs before the World Cup.”
Wales had changed the narrative of the tournament when it came from behind to defeat England 21-13 in the third round, and by remaining unbeaten it kept the destiny of the title in its own hands going into the final weekend.
With the stadium roof open to the deluge — as requested by Schmidt — Wales stormed into the lead after little more than a minute when Parkes chased Anscombe’s chip over the top to touch down.
An Anscombe conversion and three further penalties gave Wales a comfortable cushion at the break as Ireland lacked discipline and failed to find any kind of rhythm.
Ireland’s decline has been stark since it beat the All Blacks at home for the first time in history in November, and the slim chance it had of winning the title relied on beating Wales and hoping Scotland defeated England at Twickenham.
But Schmidt’s side had a mountain to climb to reverse the 16-0 half-time deficit — despite Wales having done just that in its opening match in France.
However, the mountain only got steeper after the break, when Anscombe added two further penalties, and from then on Ireland appeared a spent force.
One solitary probe got to within yards of Wales’ line midway through the half, but the men in red repelled the green invaders, and when Anscombe made it seven kicks from seven the result was virtually assured.
The home crowd’s melodic singing and deafening roars drowned out the last 10 minutes as Ireland attempted a desperate final surge. At the death Ireland manufactured a try for Jordan Larmour but the final whistle sparked jubilant Welsh celebrations.
Looking ahead to the World Cup, Gatland added: “We’re just trying to slip under the radar. We know on our day that we’re capable of beating good teams so I think we’ll have a break now and start preparing for the World Cup.
“These boys will run through a brick wall for you. They’re a really tight group and really close to each other. If we go there with a bit of luck and not too many injuries we’ve got a good chance of beating anybody.”