In 1910 the Portuguese monarchy was ousted and a republic established, and it is from this year that the current flag, and the prominence on it of the revolutionary red, that both date.

The green, often taken to express hope or the sea, can be traced back to the time of Henry the Navigator (1394-1460), who inspired and sponsored a whole generation of Portuguese maritime explorers.

The depiction of the armillary sphere at the center of the flag likewise links with Henry the Navigator, being an emblem chosen to commemorate the deeds of Henry and his protégés by King Manuel I (1469-1521), whose reign saw a further great surge in Portuguese exploration.

The main shield remembers the knights that founded and defended Portugal.

The five blue shields represent the five Moorish kings defeated by D. Afonso Henriques (1128-1185) in Ourique.

The seven castles symbolise the castles conquered from the Moors by D.Afonso III : Albufeira, Aljezur, Cacela, Castro Marim, Estômbar, Paderne and Sagres.