Maria Jesus Elorza Zubizarreta was arrested today as she disembarked from a flight from Venezuela.
An Interior Ministry statement said Elorza is wanted on a European arrest warrant issued December 2006 by French judicial authorities.
She is suspected of having belonged to an ETA unit responsible for the murder of several members of Spain's security forces before fleeing to France in 1984. There, she allegedly participated in bomb-making activities for the group before moving to Venezuela.
ETA is blamed for the killings of more than 825 people in a campaign of bombings and shootings aimed at achieving an independent Basque state straddling Spain's border with France.