The Battle of Belgium or Belgian Campaign formed part of the greater Battle of France, an offensive campaign by Germany during the Second World War. It took place over 18 days in May 1940 and ended with the German occupation of Belgium following the surrender of the Belgian Army.

On 10 May 1940, Germany's armed forces, the Wehrmacht, invaded Luxembourg, the Netherlands, and Belgium under the operational plan Fall Gelb (Case Yellow). The Allied Armies attempted to halt the German Army in Belgium, believing it to be the main German thrust. After the French had fully committed the best of the Allied Armies to Belgium between 10 and 12 May, the Germans enacted the second phase of their operation, a break-through, or sickle cut, through the Ardennes, and advanced towards the English Channel. The German Army (Heer) reached the Channel after five days, encircling the Allied Armies. The Germans gradually reduced the pocket of Allied forces, forcing them back to the sea. The Belgian Army surrendered on 28 May 1940, ending the battle.

Belgium (ⁱ/ˈbɛldʒəm/ BEL-jəm), officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO. Belgium covers an area of 30,528 square kilometres (11,787 sq mi), and it has a population of about 11 million people. Straddling the cultural boundary between Germanic and Latin Europe, Belgium is home to two main linguistic groups, the Dutch-speakers, mostly Flemish (about 60%), and the French-speakers, mostly Walloons (about 40%), plus a small group of German-speakers. Belgium's two largest regions are the Dutch-speaking region of Flanders in the north and the French-speaking southern region of Wallonia. The Brussels-Capital Region, officially bilingual, is a mostly French-speaking enclave within the Flemish Region. A German-speaking Community exists in eastern Wallonia. Belgium's linguistic diversity and related political conflicts are reflected in the political history and a complex system of government.