Johnny Sexton kicked a sensational drop-goal with the final play of a dramatic tussle with France in Paris to win the game 15-13 for Ireland.
Joe Schmidt's men dominated and controlled the Stade de France encounter for long spells but they were unable to penetrate a resolute French defence.
Four penalties from the boot of Leinster out-half Sexton had the Irish leading 12-9 as the game ticked into the final ten minutes.
In what was coach Jacques Brunel's first game in charge of Les Bleus he drew an inexperienced team together that stuck with Ireland gamely throughout an attritional contest.
All our goals would've crumbled if we'd lost.Johnny Sexton
Winger Teddy Thomas weaved his way home from 50 yards to cross the try-line and put the French ahead for the first time in the game with seven minutes to play.
Anthony Belleau missed what looked a relatively straightforward conversion and that offered Ireland hope, as they remained just one point adrift.
With their backs against the wall, Iain Henderson bravely won Sexton's restart and Ireland remained incredibly patient, edging into French territory.
With the clock already beyond 80 minutes, Sexton's daring cross-kick was taken by Keith Earls and, having gone through a mammoth 41 phases, the number ten grasped Conor Murray's pass and dropped a monster kick from more than 40 metres between the French posts to snatch victory.
Sexton admitted the kick had saved Ireland's season and he paid tribute to the mental toughness shown to craft that one final chance.
"All our goals would've crumbled if we'd lost," he said.
"I don't think we could have gone on another couple of phases, but we got there in the end.
"It says a lot about the management and that we've got some good characters in the team because it looked like it might have been deja vu. This year we had a chance and we took it thankfully."
Ireland are 2/7 to win the Six Nations this season, with defending champions England 10/3 and Wales, who thumped Scotland in Cardiff in their opener, priced at 250/1.
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