A 2-1 away win against second-placed Croatia has seen Marc Wilmots' side become the third European team to guarantee their spot in Brazil
With a game to spare, Marc Wilmots' men triumphed over the Balkan side thanks to two first-half strikes for Everton forward Romelu Lukaku, ensuring that Niko Kranjcar's 83rd minute goal did not take away three points from the visitors.
The victory means that the Rode Duivels sit top of Group A in Uefa qualification with 25 points - eight above second-placed Croatia, who also only have one game left to play.
Fellow Group A competitors Serbia have an outside chance of claiming a play-off spot thanks to Igor Stimac's side's defeat on home turf, though Scotland, Macedonia and Wales cannot reach the tournament in Brazil.
World Cup 2014 hosts, the Selecao, have already already joined in next summer's competition by Japan, Australia, Iran, South Korea, Netherlands, Italy, United States, Costa Rica and Argentina.