FRANKFURT, Germany: Slovakia caused the first upset at Euro 2024 as Ivan Schranz fired the underdogs to a 1-0 win against Belgium on Monday.
Francesco Calzona's side are 45 spots below third-placed Belgium in FIFA's world rankings.
But they made a mockery of the supposed quality gap between the teams with a courageous performance in Frankfurt.
Calzona, who also served as Napoli's interim boss in the second half of last season, had admitted he would be "delighted" with a draw.
The Italian got more than he could have dreamed of as Schranz left Belgium reeling after ending his nine-game international goal drought.
Romelu Lukaku missed a host of chances for Belgium and had a late equaliser controversially disallowed by VAR.
Slovakia's unexpected victory blew Group E wide open, just hours after Romania beat Ukraine 3-0 in Monday's other match in that pool.
It was a bitter loss for Belgium, who are in danger of once again failing to fulfil their potential at a major tournament.
Belgium's golden generation has lost much of its lustre since they crashed out of the 2022 World Cup in the group stage.
The Red Devils fell at the quarter-finals in the last two editions of the European Championship, making a third place finish at the 2018 World Cup the highwater mark of a talented but underachieving team once hailed as a potential dynasty.
Dominic Tedesco was appointed to replace Roberto Martinez in February 2023 and led Belgium on a 14-match unbeaten run heading into the Euros.
Before what was billed as a last hurrah for Belgium's veteran stars, Kevin De Bruyne had insisted they were ready to do "something good" in Germany.
But instead they reverted to type with a spluttering display that puts them under intense pressure to beat Romania in their second group game on Saturday.
Playing in a Belgian record 11th game at major tournaments, Lukaku should have bagged his 86th goal for his country in the second minute.
Jeremy Doku turned adroitly on the halfway line and accelerated menacingly into the Slovakia penalty area, where his cross was poked toward Lukaku by De Bruyne.
Lukaku looked certain to score but his close-range effort was straight at Slovakia keeper Martin Dubravka.
He threatened again moments later, only to let Doku's pass run away from him after bearing down on goal.
Slovakia punished Lukaku's profligacy to take the lead in the seventh minute.
Doku was culpable with a wayward pass as he tried to clear, allowing Robert Bozenick to cleverly backheel the ball to Juraj Kucka.
Koen Casteels saved Kucka's strike but could do nothing about the rebound as Schranz fired home from an acute angle.
Lukaku endured a nightmare evening and he again took a woefully heavy touch to waste a good chance from Yannick Carrasco's raking pass.
Belgium's angst increased in the 56th minute when Lukaku was denied by Dubravka's near-post save.
From the resulting corner, Amadou Onana looped a header over Dubravka and Lukaku slid in to score from a yard out, only for his celebrations to be curtailed as VAR ruled he was offside.
Belgium laid seige to the Slovakia goal but Dubravka saved well from Trossard and Lukaku volleyed into the side-netting before Johan Bakayoko's shot was cleared off the line by David Hancko.
And in a fitting coda to a day to forget for Belgium, Lukaku blasted home in the 86th minute but saw the goal disallowed for handball by Lois Openda in the build-up.