The national flag of Belgium (Dutch: Vlag van België, French: Drapeau de la Belgique, German: Flagge Belgiens) contains three equal vertical bands of black (hoist side), yellow, and red. The colours were taken from the colours of the Duchy of Brabant, and the vertical design may be based on the flag of France.
The national flag has the unusual proportions of 13:15, but is rarely seen. A flag in a 2:3 or similar ratio is used in most cases, even by most government bodies.The unusual proportions of 13:15 are of unknown origin.
After the death of Charlemagne, the present-day territory of Belgium (except the County of Flanders) became part of Lotharingia, which had a flag of two horizontal red stripes separated by a white stripe. The territory then passed into Spanish hands, and after the coronation of Charles V, Holy Roman Emperor yellow and red, the colours of Spain, were added. From the 16th century to the end of the 18th century, the colours of what is now Belgium were red, white and yellow. Occasionally the red cross of Burgundy was placed on the white section of the flag.
During the period of Austrian rule, a number of different flags were tried, until the Austrian Emperor imposed the Austrian flag. The population of Brussels was opposed to this, and following the example of France, red, yellow and black cockades began to appear; those being the colours of Brabant. The colours thus correspond to the red lion of Hainaut, Limburg and Luxembourg, the yellow lion of Brabant, and the black lion of Flanders and Namur.