Joe Thompson, from Cullybackey, in Co Antrim, downed a pint of Kronenbourg and declared: "We are not going home yet."
The faithful had to wait a short time for results in other games to confirm their place, but there was a party atmosphere from the minute the game against Germany ended on Tuesday with a narrow 0-1 loss.
Supporters flew from Kuwait, Beirut and the US to be at the crunch final group clash at the Parc des Princes - the Park of Princes - and acclaimed their heroes like royalty with a standing ovation at the end.
They had besieged Paris in a mass of green shirts, flags, sombreros and banners.
And long after the Germans scored a first half deadlock breaker, fans in the stadium were still "doing the bouncie" following a result which is far better than feared.
They sang "Everywhere we go it is the Ulster boys making all the noise," and the emotion poured from the solid wall of green.
The men in green chanted at their counterparts: "You only sing when you are winning," and in one corner of the stadium the cries of Deutschland were drowned out by the UIstermen.
The atmosphere was cemented by a veritable battle of the bands between supporters with rival drummers.
The First Finaghy Northern Ireland Supporters' Club from South Belfast transports its bass drum to most away matches.
Sam McClean said: "We have a carry case. We have lugged it on taxis, trains, buses, the whole lot, then we take it home on a plane.
"Oversized baggage, you see. It goes everywhere."
They took it to the Northern Ireland war memorial in France at the Ulster Tower on Monday.
"It gets the crowd going," said Mr McClean
The Euros had been fantastic, he added. "You will never get it again, the atmosphere is unreal," he said
An inflatable crocodile which has been a permanent feature of Northern Ireland's travelling entourage again showed up in the capital, and the two bass drummers from south Belfast and London led the Ulstermen in raucous full voice in the shadow of the Eiffel Tower.
A beach ball was tossed enthusiastically between fans as bemused tourists with ears echoing from the drumbeat elbowed their way through the square and towards the Seine.
Earlier, Northern Ireland fans played their counterparts in a sign of friendship and co-operation ahead of the match.
Stormont Deputy First Minister Martin McGuinness attended his first Northern Ireland game.
COMMENT RULES: Comments that are judged to be defamatory, abusive or in bad taste are not acceptable and contributors who consistently fall below certain criteria will be permanently blacklisted. The moderator will not enter into debate with individual contributors and the moderator’s decision is final. It is Belfast Telegraph policy to close comments on court cases, tribunals and active legal investigations. We may also close comments on articles which are being targeted for abuse. Problems with commenting? email@example.com