Thorgan Hazard's 20-yard swerving drive proved enough to send Belgium through to the quarter-final at the expense of defending champions Portugal.
It is likely Belgium will have to play Italy in the last eight on Friday without star man Kevin De Bruyne who left the field just after half time after suffering an ankle injury minutes before the break.
Just prior to De Bruyne's ill-fortune, courtesy of a Joao Paulhinha challenge, the less-heralded Hazard lightened up a drab first half when he came in from the left flank and, given space, let loose with an effort with the outside of his boot which deceived Rui Patricio in the flight.
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Portugal piled on the pressure in the closing stages, coming closest to scoring Raphael Guerreiro shot against the post with seven minutes remaining, less than a minute after Ruben Dias' bullet header from a corner was aimed straight at Thibaut Courtois, who gleefully parried clear.
Talking point - Belgium need to step up to down Azzuri
A lot of the match seemed a match up between a well-organised Portuguese defence preventing Belgium's quality forwards from firing, while Portugal seemed to have a lot of space to work with in the final third but did not have the quality to score or set up their talisman, Cristiano Ronaldo, who at 36 is now less capable of conjuring chances for himself.
In particular, especially with De Bruyne (and possibly Eden Hazard, who limped off in the closing stages) doubtful to play, Belgium need a bigger performance from Romelu Lukaku who, having dominated Serie A defences throughout the season, should fancy his chances against the Azzuri centre backs, but he was held in check by Pepe and Dias on this occasion.
Roberto Martinez, who famously secured an FA Cup final victory over Roberto Mancini with Wigan against Manchester City, was proved correct by opting for the ageing back three of Toby Aderweireld, Thomas Vermaulen and Jan Vertonghen, but against the different challenge of Lorenzo Insigne and, quite possibly, Federico Chiesa may opt for a more mobile option at the back.
If they are to get through Italy - where the most torturous route to a potential final would likely see them face France - they must not let go of control of the game as they did in the second half against Portugal. It is hard to see the Azzuri being quite as wasteful.
Man of the match - Thorgan Hazard (Belgium)
Seen mainly as an after thought for club and country, with the hardest brother to be compared to since Jack Charlton, this was the Borussia Dortmund midfielder's moment to shine.
In a game without a real star performer, Eden's younger brother worked tirelessly in up and down the left flank helping his side to snuff out much danger on Portugal's right wing.
While it is possible to question Rui Patricio for getting beaten by an effort which was far from the corner of the net, Hazard's effort was fantastic and shone on a night where there was not enough quality to match the stars on show.
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Belgium: Courtois 7; Alderweireld 7, Vertonghen 7, Vermaelen 7; Meunier 7, Tielemans 6, Witsel 7, T. Hazard 8*; De Bruyne 6, E. Hazard 7, Lukaku 5.
Subs: Mertens 6, Carrasco 6, Dendoncker 6.
Portugal: Patricio 5; Dalot 6, Dias 7, Pepe 6, Guerreiro 7; Moutinho 6, Palhinha 6, Sanches 7; Bernardo 6, Diogo Jota 5, Ronaldo 7.
Subs: Felix 6, Fernandes 5, Silva 6, Pereira 6, Oliveira 6.
43' GOAL! That came from nowhere. Hazard - the other Hazard, Thorgan, smashed a rocket drive from outside the left hand side of the penalty area. Swerving shot with the outside of his right foot baffled Rui Patricio.
82' - Dias meets Fernandes' cross with a fierce header but Courtois parries away from danger. Anywhere else in the goal but straight at the keeper and that is a goal.
83' - Guerreiro hits the post with a low drive from the edge of the box that had Courtois beaten. It came after a deep cross for Ronaldo was half-cleared.
88' - This time Ronaldo flicks on and the sliding Silva at the far post is so close to squeezing the ball past Courtois.
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