Portugal’s national flag includes a yellow armillary sphere and a shield on a red and green field.
The flag was adopted on June 30, 1911, after Portugal became a republic in 1910. Green occupies the hoist side and red the fly side. The armillary sphere, a historic astronomical instrument, recalls Portugal’s maritime exploration and the country’s role in the Age of Discovery.
The central shield contains five smaller blue shields arranged in a cross, each traditionally bearing five bezants. A red border around the shield contains seven castles, symbols associated with Portugal’s history and the Christian reconquest of territory. The exact symbolism of some elements has been debated, but the design deliberately connects the republic with older Portuguese national imagery.
The flag’s vertical green-red division is sometimes mistaken for a simple political color scheme. Its emblem is the key identifying feature: Portugal is the national flag most closely associated with the armillary sphere.