The national flag of the Principality of Andorra was adopted in 1866. The flag is a vertical tricolour of blue, yellow, and red with the coat of arms of Andorra in the center. Although the three vertical bars may at first appear to be of equal width, the center yellow bar is slightly wider than the other two so that the ratio of bar widths is 8:9:8. The overall flag ratio is 7:10.
The design is related to the flags of France, Spain, Catalonia and Foix, the lands historically linked with the small country. A flag of three bars is similar to that of the French Tricolour, while the pattern of a wider middle stripe can be noted on the Catalan flag (as the old royal symbol of the Crown of Aragon) and on the arms of the old County of Foix (currently part of France). The blue and red of the Andorran flag are also found on the French flag, with red and yellow also being the principal colours of the colors of the other two flags. From 1806 to 1866, Andorra's flag was a vertical bi-colour of yellow and red. The motto in the coat of arms in the middle stripe Virtus Unita Fortior means "Virtue United is Stronger".
The design is similar to the flags of Romania, Moldova, and Chad. All of these are vertical tricolours of blue, yellow, and red, but unlike that of Andorra, their flags have all stripes of equal width.