Martin de Azpilicueta Jauregizar was born in Barasoain, Navarre, on December 13, 1491 into an influential Navarrese family. He began studying for a degree in theology at the University of Alcalá de Henares in Castile. However, when the Kingdom of Castile invaded and conquered the Kingdom of Navarre in 1510 he fled, together with his family (which was loyal to the ruling royal house of Navarre), to Toulouse in the Kingdom of France.
In 1518 he obtained a doctorate in canon law from the University of Toulouse. He was ordained a priest, likewise, in Toulouse, and in 1523 returned to Navarre, spending time at the Augustinian monastery in Orreaga (Roncesvalles-Roncevaux). Between 1524 and 1538, Azpilicueta served in several canon law chairs at the University of Salamanca. Thereafter, he taught at Coimbra University in Portugal for a further sixteen years before retiring. He then returned to Navarre, where he took on the responsibility of raising three of his orphaned nieces. A decade later, in 1568, he went to Rome to help defend Bartolomé Carranza, the Archbishop of Toledo, in a protracted trial before the Inquisition. While there, Azpilicueta also served as an advisor to Pope Gregory XIII and Pope Sixtus V, and he eventually died in Rome in 1586 at the age of ninety-three.
Also known by the epithet Doctor Navarrus (The Navarrese Doctor), Azpilicueta became enormously influential in the field of canon law and ethics, earning a reputation as a humble, prudent, and erudite scholar. Throughout his life he turned down several opportunities to occupy high-ranking church positions, preferring instead to dedicate his time to scholarly inquiry and offering legal advice. His Manual de confesores y penitents (Manual of confessors and penitents, 1553) was especially significant, marking an important milestone in the emergence of moral theology as a discipline in its own right. Therein, Azpilicueta also addressed issues such as exchange, supply, and demand, as well as the phenomenon of money, leading some observers to regard the text as a pioneering work of early economics.