The opening 15 minutes saw both teams attempting to work the other out, using their time on the ball tactically.
But it was never going to stay that way as the game opened up.
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However, it was Belgium's Thorgan Hazard who broke the deadlock shortly before the half-time whistle. The younger brother of Eden set himself for a stunning 20-yard strike that swerved its way past Rui Patricio.
Early in the second half, Belgium suffered a setback as Kevin De Bruyne went down with an injury and had to be replaced.
Tempers flared and cards were shown as Portugal cranked up the pressure and the last 10 minutes saw Belgium with their backs to the wall.
Raphael Guerreiro hit the post, while Ruben Dias headed a good chance straight at Courtois but Belgium hung on.
For the full report, check out our sister site Football365.
Stat of the day
What's next for Belgium?
Belgium will now face Italy in the quarter-finals on Friday, July 2 at 20:00 BST in Munich.