Basque (Euskara) is one of the oldest languages in Western Europe, preceding the Indo-European tongues.
Various scholars claim that there exist nexus between Basque and Iberian, Berber or some of the languages found around the Caucasus, but the origins of Euskara remain a mystery.
https://www.eke.eus/en/kultura/euskara-the-basque-language/history-of-euskara