The Cardiff Blues wing, who was a British & Irish Lions tourist in South Africa in 2009, was inches short of steering Wales into the World Cup final in Auckland with a last gasp kick against the French.
But this time he was right on the mark when presented with a match-winning penalty in the 79th minute after English referee Wayne Barnes penalised Stephen Ferris for a dangerous tackle.
Wales had scored three tries, and taken the lead twice earlier on, before Halfpenny, who took over the goalkicking duties from Rhys Priestland, got his shot at glory.
"It was the hardest kick I've had to take in my life. Having to deal with the miss against France in the World Cup semi-final was difficult, but this makes it all worthwhile," admitted Halfpenny.
Ferris became the second player in the game to receive a yellow card for dangerous play, Wales lock Bradley Davies being binned in the 65th minute for dumping replacement Donnacha Ryan on his back, and his indiscretion paved the way for Wales to steal a third successive win over the Irish for the first time since the Seventies.
While Wales scored three tries - two from Jonathan Davies and one from the magnificent George North - the Irish crossed their visitors' line once in each half. Tommy Bowe paved the way for his former Ulster team mate Rory Best to edge Ireland 10-5 ahead at the break.
Then Bowe rounded off a period of intense pressure when Wales were down to 14 men with a corner try to put Ireland six points clear with 10 minutes to go. Jonny Sexton was inches wide with his touchline conversion attempt and Wales patiently built their way back into the game.
Then North struck in the left corner with a try that crowned a wonder display and this time Halfpenny was just wide. That left Wales a point behind with three minutes left to play.
They won the ball, kept it and drove to within 30 metres of the home line when Ferris was penalised for upending Ian Evans. Up stepped Halfpenny and over went the matchwinning penalty.