Ireland's women dashed Welsh Triple Crown dreams to set up a Six Nations title tilt with a superb performance in Swansea.
The visitors' points came courtesy of tries from prop Ailis Egan and wing Alison Miller, with the reliable boot of full-back Niamh Briggs contributing 10 points, with two conversions and two penalties.
But this 20-0 victory was secured by a tenacious defensive effort.
Tom Tierney's girls can win the Triple Crown by beating Scotland on the road this weekend, but they can also clinch the title after moving level on points with a French side whose chances of a clean sweep were ended in Italy.
France have the better points difference, but also have the more testing final fixture in England.
A desperate Welsh defence had repelled one extended Irish onslaught, but their pack rumbled their way up to the line with a composed drive and Egan made the short burst to power over by the posts, with Briggs adding the conversion.
Wales duo Shone Powell Hughes and Sioned Harries made yards with some powerful carrying after Elinor Snowsill's clever kick.
But the green wall did not break and when Claire Molloy won a key turnover, the siege was lifted and Ireland went to the changing rooms in front.
Briggs extended that lead with her first penalty and she had another chance after Wales went off their feet at a ruck. The Ireland full-back's strike was perfectly judged to make it 13-0.
Wales went close when wing Elen Evans broke through, but she could not beat the final defender, before Miller applied the coup de grace, speeding past two defenders to seal the win.