There's always been a degree of friendly tension between the two, with France regarding Belgium, and its French-speaking Wallonia region, as something of a poor cousin, while the Belgians often dismiss France as patronising and faux-superior.
It's a showdown between "Asterix" and "Tintin". Les Bleus (The Blues) versus Les Diables Rouges (The Red Devils). France against Belgium. The World Cup equivalent of a local derby, with a heavy dose of national rivalry thrown in.
In France, sports shops were rapidly selling out of the national soccer strip on Tuesday as fans got ready for the semi-final showdown in St. Petersburg. In Belgium, mad-keen Diables Rouges supporters were jumping on last-minute flights to Russia.
Bars, cafes and restaurants in Paris and Brussels were preparing for a bumper evening of revelry.
There's always been a degree of friendly tension between the two, with France regarding Belgium, and its French-speaking Wallonia region, as something of a poor cousin, while the Belgians often dismiss France as patronising and faux-superior.
But those frictions, which extend from food to comic strips (Do you prefer France's "Asterix" or Belgium's "Tintin"?) to language pronunciation, will be ramped up to breaking point when their respective teams take to the field at 1800 GMT (2330 IST).
Adding to the rivalry is the fact that Thierry Henry, a hero of French soccer who helped the nation to World Cup glory in 1998, is now an assistant manager with Belgium's national team and will stand on their touchline on Tuesday. On social media, Henry has been vilified by many French fans as a "traitor".
"His heart will be divided," France captain and goalkeeper Hugo Lloris told French media on Monday. "He is above all French. But tomorrow, as a professional, he will be channelling all his passion into the Belgian team."
Some of the Belgian team grew up playing in France. There are members of each squad who play for the same club but will be on opposite sides of the ball tonight. They all speak, or at least understand, the same language.
"A Duel Between Friends" declared France's Journal du Dimanche newspaper on Sunday, with a cartoon on the front page taken from the comic book "Asterix in Belgium", when the plucky Gauls encounter a rival tribe from across the border.
The editor of Belgium's L'Echo was having none of the French talking down to its smaller neighbour, especially as the current Belgian team is regarded as the greatest in a generation, with the best chance ever of bringing home the cup.
"The 'Little Belgians' aren't little any longer," he said in an editorial headlined "Belgium in the final".
Newspaper cartoonists have spent the last few days skewering one another's national stereotypes, whether over food, language or attitude. With 11 million Belgians to France's population of 67 million, there's often a subtext of inferiority/superiority.
One place where residents have no choice but to put those differences to one side is Comines, a town that sits right on the Franco-Belgian border, split by the river Lys.
Reached by phone, a bar owner in French Comines said the atmosphere in the town is convivial ahead of the game.
Asked whether he was expecting lots of fans to come to his bar to watch, he replied: "Well, the Belgians have put up a big screen TV in the square on their side, so we'll probably all go there."
