Called the Ikurriña, a flag designed as a national symbol of the Basque Country by the founders of the Basque Nationalist Party EAJ-PNV Luis and Sabino Arana.
The flag was designed in 1894 for the province of Biscay in a set of one flag for each of the seven Basque provinces. However, since PNV activity was mainly confined to Biscay, only the Biscayne flag caught on. It was adopted as the flag of the whole autonomous Spanish community of the Basque Country in 1933 and 1980. It is now also commonly used in the French Basque Country.
The Ikurriña has a white cross and a green saltire across a red background. The green St Andrew's cross might represent the Oak of Guernica. The white cross represents Catholicism and was also found behind the Oak in the Heraldic arms of Bizkaia, and the red background represents the Basque people. In this way, red, white and green have become the national Basque colors.
The name was intended to have the generic meaning of "flag" but ended with this specific meaning. The current standard Basque word for "flag" is the Castillian Spainish "bandera. "
Regional Flags of Spain