Portugal’s flag is divided vertically into green and red and carries an armillary sphere with the national shield at the boundary between the colours.
The present design emerged after the 5 October 1910 revolution that ended Portugal’s constitutional monarchy. Green and red were associated with the Portuguese republican movement, and the new flag was officially adopted on 30 June 1911. Green occupies the hoist side, while red extends across the larger fly-side portion.
The central armillary sphere is more than decoration. It was a navigation and astronomical instrument closely associated with Portuguese seafaring and the Age of Discovery. It had already been used in Portuguese royal symbols for centuries before appearing on the republican flag.
The shield above the sphere preserves older Portuguese heraldry. Its five blue shields and surrounding castles connect the republic to the country’s medieval monarchy and foundational traditions. The flag is often confused with Ireland’s, but Ireland has an evenly divided green-white-orange tricolour and no central coat of arms.