A knock of 142 off of 128 balls from Paul Stirling helped Ireland to a seven wicket victory over England at Southampton.
A pair of defeats over the past week at the Ageas Bowl meant a series victory was beyond Ireland.
And when Saqib Mahmood's wicket fell leaving the world champions with a total of 328, a win on their final outing appeared unlikely.
The wickets of openers Jason Roy and Jonny Bairstow had gone for the addition of just 5 runs, putting Ireland in a positive frame of mind.
But Dubliner Eoin Morgan top-scored for the hosts with 106 off just 84 balls to steady the ship.
Needing 329 to win, but knowing their were runs to be had off the Rose Bowl pitch, Andy Balbirnie's side set about their task with relish.
The loss of opener Gareth Delaney with the final ball of the eighth over from David Willey did little to shake Stirling.
Balbirnie and he put on a stand of 214 before Stirling was run-out by the combination of Tom Curran and Roy.
Ireland were clever in how they chased down that total of 329, hitting nine fewer 4's and one less 6 than their world champion hosts.
Harry Tector - playing his first international series - joined Balbirnie at the crease before the skipper departed 15-runs later with a personal tally of 113.
Enter Kevin O'Brien - so often the focal point of Ireland's finer days in the middle.
Together he and Hector put together a partnership of 50 to get Ireland over the line, with the 36-year old striking the winning runs.
— Cricket Ireland (@Irelandcricket) August 4, 2020
Along with the honour of beating the world champions at their own game, in their own back garden, the win boosts Ireland's hopes of qualifying for the 2023 World Cup.
Balbirnie's men pick up their first points of the ICC World Cup Super League.
"It was brilliant to get our first win of the competition," Stirling said upon receiving his man of the match award, "Especially after a couple of tough games, [we] showed a lot of character to come back.
"We've chased over 300 a number of time, particularly in World Cups, so we knew we could do it, it freed us up to go hard at the top, have a bit of fun and it was a solid chase in the end.
"We haven't played for so long, you get used to sticking your pads on having some nerves and then you get back to normal.
"Love batting with Bal[birnie], we seem to put on good partnerships. Great to bat with and his knock was pretty special as well."
Asked how the victory ranks with some of their World Cup exploits, Stirling said, "This is up there, definitely, against England in England, nice knock to have but it's the win and the team that counts."