Ireland paceman Peter Connell destroyed Worcester, taking 5-19
Worcestershire crashed out of the Friends Provident Trophy after being bowled out for the lowest one-day score in their history by Ireland.
Needing a win to finish top of Group A, the home side looked on course when they bowled out the Irish for 152.
But they were then sensationally bowled out for just 58 to lose by 94 runs.
Kiwi Peter Connell took 5-19 as Steve Rhodes' side slumped from 20-1 to 21-6 - and Worcester never recovered, Daryl Mitchell being left stranded on 15.
Worcestershire began the day second in Group A and looking for a win to ensure a home quarter-final on Saturday.
But they ended up finishing third in the group and missing out on the quarter-finals completely, thanks to Hampshire's equally stunning 10-wicket win over Nottinghamshire at Trent Bridge.
This was Ireland's day, though, and the country's cricketers (made up of five Irishmen, three Aussies, two New Zealanders and a Londoner) received a standing ovation at New Road.
It was their first win in 12 games in this competition since beating Warwickshire in Belfast in 2008.
Worcestershire's previous lowest one-day score was 70 against Gloucestershire in a Benson and Hedges Cup qualifier, also at New Road in April 2002.
FP TROPHY QUARTER FINALISTS
GROUP A: Hampshire (winners), Nottinghamshire
GROUP B: Somerset (winners), Middlesex
GROUP C: Gloucestershire (winners) Sussex
GROUP D: Lancashire (winners), Essex
Ireland, who lost by 52 runs when they Worcestershire in Belfast last month, had never previously bowled out a county for less than a hundred. But they stunned the New Road crowd by bowling out the home side in 20.3 overs.
The Irish had themselves been on trouble on 75-6, only to be rescued by a stand of 57 for the seventh wicket between Kyle McCallan (40) and Trent Johnston (39).
But woeful Worcestershire soon hit massive problems, as Connell grabbed his five wickets for a mere three runs in the space of just 14 balls.
He began in sensational style by ripping out home skipper Vikram Solanki.
Then, from 20-1, the home side truly buckled as Connell also removed Worcester's other opener Stephen Moore and Moeen Ali, bowled first ball.
Kevin O'Brien heaped on the pressure by trapping Alex Kervezee leg before. But Connell regained the spotlight by also removing Steven Davies and Gareth Batty to leave home hopes in tatters on 21-6.
Mitchell tried to repair the damage in a 29-run stand in 10 overs with Ashley Noffke, but he holed out to square leg off fellow Aussie Johnston.
And both Johnston and another of their Australians Alex Cusack claimed two wickets apiece as unfancied Ireland finished things off - to register embarrassed Worcestershire's lowest total in 46 years of one-day cricket.
Worcestershire director of cricket Steve Rhodes told BBC Hereford and Worcester:
"The only thing I can say to all our supporters and members is I am deeply upset and apologise to them all because that performance was just not good enough for a professional side.
"Each and every one of us has to take a responsibility, the players and myself, as we are better than that.
"We had a massive prize to be gained from a win today and we didn't do ourselves justice."
Ireland's bowling hero Peter Connell told BBC Hereford and Worcester:
"We've got a good bowling outfit so once we were over 130 or 140 we were always in with a sniff.
"We always had to take early wickets and then keep taking wickets because all of these county sides are professional enough that the middle and lower order can finish games.
"So it was always important for us to keep taking wickets."
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