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 victory was secured by a tenacious defensive effort, which kept the home side scoreless and kept Ireland on top during a key period just before the break.
Tom Tierney's girls can win the Triple Crown by beating Scotland on the road next 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.
Ireland may well find themselves thankful for the clean sheet they kept here.
They saw off an early period of pressure from a fired-up home side, but slowly turned the screw as time went on.
A desperate Welsh defence had just about repelled one extended Irish onslaught, but they could not survive a second.
The Irish 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 simple conversion.
Then came the key passage of play. Wales responded strongly to falling behind, with No 8 Shone Powell Hughes and openside Sioned Harries making yards with some powerful carrying after Elinor Snowsill's clever kick had penned Ireland on their own line.
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 soon extended that lead with her first penalty and she had another chance some 15 minutes later after Wales went off their feet at a ruck.
Once again, the Ireland full-back's strike was sweet and perfectly judged to make it 13-0.
Wales battled and went close when wing Elen Evans broke through, but she could not beat the final defender, before Miller applied the coup de grace, snapping up a loose ball and speeding past two defenders to seal the win.
Wales - D Hywel (K Lake 50); L Harries, A Taviner, G Rowland, E Evans; E Snowsill (H Jones 78), A Day (K Bevan 78); J Davies (C Thomas 50), C Phillips (A Lawrence 75), C Edwards (A Evans 58), J Hawkins (R Rowe 75), R Taylor, S Williams (M Clay 78), S Harries, S Powell Hughes.
Ireland - N Briggs; H Tyrrell (A Doyle 78), J Murphy, J Shiels (S Naoupu 18-28), A Miller; N Stapleton (S Naoupu 66), L Muldoon (T Rosser 53); R O'Reilly (F Hayes 53), G Bourke (S Mimnagh 78) A Egan (F O'Brien 78), S Spence (K Norris 78), ML Reilly, P Fitzpatrick, C Molloy, H O'Brien (O Fitzsimons 36).
Ref - C Hodnett (RFU)