Portugal’s flag places the national shield over a yellow armillary sphere. Together, these form the central emblem on the boundary between the flag’s green hoist and red fly sections.
The armillary sphere recalls Portugal’s maritime expansion during the Age of Discoveries. It was a navigation and astronomy instrument, and King Manuel I adopted it as a personal symbol in the early 16th century. Its presence on the modern flag connects the republic with Portugal’s seafaring history.
The shield is older than the sphere in Portuguese heraldry. Its five blue escutcheons and surrounding castles developed through the medieval monarchy and are associated with Portugal’s history, royal authority, and traditional legends. The current flag was introduced after the 1910 republican revolution and officially adopted in 1911.
A common mix-up is Brazil: Brazil’s flag has a celestial globe and stars, but not Portugal’s shield-and-armillary-sphere emblem. The sphere also appears in Portuguese architecture, including Lisbon’s Jerónimos Monastery and Belém Tower.