Leizarraga was born in the
Northern Basque Country in the province of
Labourd in a village called
Briscous in 1506. Although the village was in Labourd, it fell within the area of the
Lower Navarrese dialect of Basque. His family's farmhouse bore the family's name, Leizarraga, and stood in Briscous until it was destroyed in 1944. Very little is known about Leizarraga's early years beyond these few facts.
Leizarraga was baptised a
Catholic. Although it is not known where he trained, he was trained as a priest and converted to
Protestantism in 1560. By 1563, his name is mentioned in the records of the Protestant Synod of
In his dedication of the New Testament to
Jeanne d'Albret he mentions having spent time in prison but again, it is not known which prison he was in, what the charge was or how long he was imprisoned for.
He was instituted as
rector of the church in
Lower Navarre in 1567 by Jeanne d'Albret. By the time Leizarraga came to Bastide, the majority of inhabitants were no longer speaking Basque but had switched to speaking
Gascon. Nonetheless, Leizarraga was even in his time renowned as a great scholar of the Basque language, the very reason he would later be entrusted with the translation of the New Testament. It is also known that various Basque shepherds in the area sent their children to him so that he would teach them Basque.
He was married but it is not known when or to whom.
In March 1563 Leizarraga was instructed by
Jeanne d'Albret, the Queen of
Navarre at the Synod of Béarn to produce a Basque translation of the New Testament. Having negotiated the tricky issue of translating into a language which by then had no great written tradition, common standard or spelling system, he persevered with some help from four old Catholic colleagues: Piarres Landetxeberri from
Espès-Undurein, Sanz de Tartas from
Charritte-de-Bas (both in
Soule), Joanes Etxeberri from
Saint-Jean-de-Luz and a Mr Tardets who was a minister in
Ostabat. Finally, in 1571, the printer Pierre Hautin based in
La Rochelle printed three works by Leizarraga, amongst them is translation of the New Testament.
It is indicative of the respect he commanded that in 1582 he was visited by
Jacques Auguste de Thou, the man who would later negotiate the
Edict of Nantes on religious tolerance. In his writings, Thou mentions Leizarraga and the copy of the Basque translation of the New Testament he had been given as a gift during his visit. This copy today is in the
National Library of France.
It is also Thou who mentions the exceptionally harmonious relationship between Protestants and Catholics in Bastide where according to him both faiths were worshipped in the church, something that was rare in 16th century France which is known for its
By 1594 Leizarraga was no longer attending the Synod of Béarn, the record stating Monsieur de Lissarrague, ministre de Labastide de Clarence, excusé pour sa vieillesse et pour son indisposition "Mr Liazarraga, minister of Bastida, makes his excuse due to old age and being indisposed.
 He died in Bastide in 1601 at the age of 95.