Ireland 16-16 Wales
Johnny Sexton kicked a penalty six minutes from time to preserve injury-hit Ireland's unbeaten Six Nations home record under Joe Schmidt and stall Wales' stirring fightback.
A 16-16 draw - the first between Ireland and Wales since 1991's 21-all match at Cardiff Arms Park - meant that both sides' Grand Slam hopes foundered at the first hurdle, yet they played with such fearsome commitment and intensity to still suggest strong title ambitions.
Ireland led 13-0 at the Aviva Stadium after 30 minutes through scrum-half Conor Murray's try and eight points from Sexton, but Wales hit back through a Taulupe Faletau touchdown, plus three Rhys Priestland penalties and a conversion after he replaced injured World Cup hero Dan Biggar.
Wales led by three points with time running out, but Sexton - as he has done on so many previous occasions - came up trumps when it mattered and ensured that Ireland avoided defeat.
A draw was arguably the fairest result, given that both teams did their utmost to batter each other into submission and neither deserved to taste defeat.
It probably means that Eddie Jones' England are the opening weekend's winners, yet both Ireland and Wales will move forward in the tournament with confidence on this evidence, both believing that silverware is achievable.
Ireland head coach Schmidt will take heart that his side could still perform, given the absence of nine front-line players, while Wales erased memories of a crushing 26-3 loss on their last Six Nations visit to Dublin in 2014.
Wales were forced into a late change, with full-back Gareth Anscombe sidelined because of a tight hamstring. Liam Williams, who had played barely 60 minutes of rugby since the World Cup due to a foot problem, replaced him.
Elsewhere, wing Tom James made his first Wales appearance for more than five years, while Ireland handed a debut to South Africa-born Munster flanker CJ Stander, but a number of injuries meant they were without star names like Rob Kearney, Tommy Bowe, Cian Healy and Sean O'Brien.
Ireland, though, made a bright start that Sexton converted into points with a fifth-minute penalty, before Wales stirred through some sustained attacking play that had centre Jamie Roberts at its forefront.
But as in the World Cup, Wales were guilty of not taking try-scoring opportunities out wide, and Ireland regrouped to launch another period of pressure sparked by full-back Simon Zebo's break out of defence, before a second Sexton penalty doubled their lead.
Biggar, his left foot heavily strapped after taking an early knock, then sent an angled penalty attempt wide, but there was no immediate sign of him being removed from the action despite his movement clearly being restricted.
Wales' coaching staff eventually hauled Biggar off after 22 minutes and the visitors struggled to regroup, with Stander going close to a try, but television match official Graham Hughes did not find in their favour.
But Ireland did not have to wait much longer, as further sustained pressure driven by Stander and lock Devin Toner resulted in Murray crashing over from close range, with Sexton's conversion putting Ireland 13-0 ahead and full value for such dominance.
Wales opened their account through a 31st-minute penalty following a dangerous Keith Earls tackle on Williams, then centre Jonathan Davies' clever kick into space gave the visitors their most threatening territorial position of the half.
And after three powerful scrums, Wales turned pressure into points when Faletau broke off the back and finished superbly, claiming a try that Priestland converted and slashing Ireland's lead to 13-10 at the break.
Priestland hauled Wales level through a 46th-minute penalty, but the Bath back then infringed, conceding a penalty when he deliberately knocked on. Sexton, though, kicked for the corner and Ireland's forwards looked to capitalise.
Wales managed to thwart the threat, though, and entering the final quarter there remained nothing to choose between the teams, both in terms of the scoreboard and every key area.
Wales boss Warren Gatland sent on both replacement props - Gethin Jenkins and Tomas Francis - by the hour mark, yet Ireland looked more dangerous with ball in hand, which was underlined when an arcing Sexton break almost resulted in wing Andrew Trimble crossing wide out.
The alarm bells were ringing for Wales, yet their aggressive defence ensured they retained a foothold near halfway before going through several patient phases of play as they probed for an opening.
It was tight, tense, attritional rugby as both sides continued to batter away at each other like heavyweight boxers, before Priestland edged Wales ahead for the first time with seven minutes left.
But the lead lasted barely two minutes, with Wales infringing 40 metres out and Sexton found the target to tie things up once more and ensure a nerve-shredding final five minutes.
Priestland sent a drop-goal chance wide after 77 minutes, and that was the final opportunity as referee Jerome Garces' whistle signalled the end of a gripping contest.
Breaking team news
Wales have announced that Gareth Anscombe has a tight hamstring and has been ruled out of the match so Liam Williams takes his place at full-back, having been flown into Dublin this morning. Revised teams:
Ireland 15 Simon Zebo; 14 Andrew Trimble, 13 Jared Payne, 12 Robbie Henshaw, 11 Keith Earls; 10 Jonathan Sexton, 9 Connor Murray; 1 Nathan White, 2 Rory Best (capt), 3 Jack McGrath, 4 Mike McCarthy, 5 Devin Toner, 6 CJ Stander, 7 Tommy O'Donnell, 8 Jamie Heaslip.
Replacements 16 Sean Cronin, 17 James Cronin, 18 Tadhg Furlong, 19 Donnacha Ryan, 20 Rhys Ruddock, 21 Kieran Marmion, 22 Ian Madigan, 23 Dave Kearney.