Wales Training - EURO 2016
The two sides met in their qualification campaigns and it was Wales who came out on top when the two sides met overall. They played out a 0-0 draw in Brussels while a solitary Gareth Bale goal settled the game in Cardiff.
Wales have had a magnificent tournament and can already call it a success with their progression to the last eight, and the last of the home nations to remain in the competition but they don't want the journey to end here. After two wins and a loss from the group stage, Wales were handed a last-16 tie with Northern Ireland - which they managed to squeeze their way through.
Belgium now seem to be finding their form after their opening game loss to Italy. They dispatched the Republic of Ireland with relative ease before confirming their place in the knock-out stages with a narrow win over Sweden. Their 4-0 win over Hungary was the most comprehensive victory in the tournament so far, and possibly the most impressive performance from any side in the competition.
They did however suffer a blow when Tottenham's Jan Vertonghen picked up an ankle injury that could keep him out for up to eight weeks - meaning Jordan Lukaku could come into the side.
So, here are three players to watch in what is sure to be an intriguing encounter:
Wales' Ashley Williams
It seemed as if the Wales and Swansea captain was struggling with a shoulder injury during the win over Northern Ireland in the last round, but the signs are that he should be fit to lead the side out for tonight's crunch fixture.
Wales were excellent defensively in their two games against Belgium in qualifying and they are going to need another fine display from their captain if they are to make it to the last four tonight.
Belgium's Eden Hazard celebrates after scoring their third goal
The Belgium captain has started to show signs of coming alive in this tournament, especially in the last round where he was excellent in their demolition with Hungary. Much like his season with Chelsea, he seems to be coming good late on - which is ideal in a tournament scenario.
There are still one or two question marks surrounding his future - with Real Madrid linked with a move for him this week by the Daily Mirror - and a good performance tonight could add fuel to those rumours. However, there seems to be little indication that he's agitating for a move, and he seems fully focussed on the job at hand for his country.
Wales' Aaron Ramsey in action
While all the eyes of the Belgium defence will be on Gareth Bale as he the main goal threat for Wales, Ramsey has a pivotal role in running the Belgian midfield ragged, providing service, and trying to get come away with a goal himself.
It was a job he did very well against Russia, though Belgium are at a significantly higher level in terms of ability. Keeping hold of possession, and providing that supply line is going to be key for Wales tonight if they are to succeed.