Sporting Lisbon's Pedro Goncalves scored an incredible equaliser and the Portuguese team went on to knock Arsenal out of the Europa League with a 5-3 penalty shootout victory in Thursday's last 16 second leg.
Sporting trailed when Granit Xhaka gave Premier League leaders Arsenal the lead in the first half at the Emirates Stadium.
But Portugal midfielder Goncalves forced extra-time when he beat Arsenal keeper Aaron Ramsdale with a breathtaking strike from 46 yards out.
Goncalves's audacious goal was reminiscent of David Beckham's long-range chip for Manchester United against Wimbledon that launched him to superstardom in 1996.
With reality television star Kim Kardashian and her Arsenal fan son Saint watching from the stands, a pulsating encounter ended level at 1-1 on the night and 3-3 on aggregate, requiring penalties to settle the tie.
It was Sporting who emerged with a shock victory as Gabriel Martinelli's effort was saved by Antonio Adan and Nuno Santos dispatched the winning kick.
"A huge blow obviously. There were moments in the first 75 minutes where we weren't at our level. We gave every ball away and we didn't have the capacity to take the game," Arsenal manager Mikel Arteta said.
"We had big chances to finish the game. We have to look at ourselves and why we were not good enough to go through."
Adding to Arsenal's problems, defenders William Saliba and Takehiro Tomiyasu limped off injured in the first half after Arteta tried to protect his key players by making five changes.
Arsenal haven't won a European trophy since lifting the Cup-Winners' Cup in 1994 and their wait will go on for another year.
But the Gunners would gladly swap Europa League success for a long-awaited Premier League title.
Arsenal sit five points clear of second placed Manchester City in the Premier League as they chase a first title since 2004.
"We have 11 games left. Our next game with Palace is a final. All the work we do right now has to be towards Palace. We have to be better than this game," Arteta said.
Arteta had fielded a strong side in the first leg in Lisbon, but was more cautious ahead of Sunday's Premier League clash with Crystal Palace, resting Bukayo Saka, Martin Odegaard, Leandro Trossard, Ben White and Thomas Party.
BEWILDERED RAMSDALE
Arteta's one concession to Arsenal's attempt to reach the last eight was including Brazil forward Gabriel Jesus for his first start since undergoing knee surgery following his injury at the World Cup last year.
Jesus, who came off the bench against Fulham on Sunday for his first appearance since the injury, nearly marked his return with a goal as he stretched to reach Reiss Nelson's cross, forcing Adan to save at full stretch.
Arsenal moved ahead in the 19th minute when Gabriel Martinelli got behind the Sporting defence for a shot that was parried out by Adan, with Xhaka lashing in the rebound from 12 yards.
The sight of Saliba limping off moments later dampened the celebrations of Xhaka's fifth goal this season.
Arteta had seen enough of Arsenal's injury problems and took off Jesus at the interval to preserve his star striker.
But Sporting mounted a strong showing in the second half and their pressure was rewarded in stunning style in the 62nd minute.
When Jorginho lost possession in the centre circle, Goncalves seized his chance, looking up to see Ramsdale off his line before unfurling an incredible lofted strike from just inside the Gunners half that arrowed over the Arsenal keeper and dipped in under the bar.
Ramsdale sat bewildered in the back of his own net and shell-shocked Arsenal almost conceded again when Paulinho headed just over.
Sporting's Marcus Edwards and Arsenal substitute Trossard both spurned glorious chances to win it before Lisbon's Manuel Ugarte was sent off for a second bookable offence when he clattered into Bukayo Saka in the 118th minute.