"Gernikako Arbola" is the title of a song in bertso form presented both in Madrid (1853) and by the shrine of Saint Anthony at Urkiola (1854) by the Basque bard José María Iparraguirre, celebrating the Tree of Gernika and the Basque liberties. The song is the unofficial anthem of the Basques, but only the first stanza is sung as the Basque anthem. In 2007, the General Assembly of Biscay declared it the district's official anthem.

Gernikako Arbola is an oak tree that symbolizes traditional freedoms for the Biscayan people, and by extension for the Basque people as a whole. The Lords of Biscay swore to respect the Biscayan liberties under it, and the modern Lehendakari of the Basque Country swears his charge there.