Saint Eucherius, bishop of Lyon, (c. 380 – c. 449) was a high-born and high-ranking ecclesiastic in the Christian Church of Gaul. He is remembered for his letters advocating extreme self-abnegation. Henry Wace ranked him "except perhaps St. Irenaeus the most distinguished occupant of that see".
On the death of his wife Gallia (born c. 390), as was a common 5th century practice, he withdrew for a time to the monastery of Lérins, founded by Saint Honoratus on the smaller of the two islands off Antibes, with his sons, Veranius and Salonius, to live a severely simple life of study and devote himself to the education of his sons. Soon afterward he withdrew further, to the neighbouring island of Lerona (now Sainte-Marguerite), where he devoted his time to study and mortification of the flesh. With the thought that he might join the anchorites in the deserts of the East, he consulted John Cassian, the famed hermit who had returned from the East to Marseille; Cassian dedicated the second set of his Collationes (Numbers 11-17) to Eucherius and Honoratus. These Conferences describe the daily lives of the hermits of the Egyptian Thebaid and discuss the important themes of grace, free will, and Scripture. It was at this time (c. 428) that Eucherius wrote his epistolary essay De laude Eremi ("In praise of the desert") addressed to Bishop Hilary of Arles.
Though imitating the ascetic lifestyle of the Egyptian hermits, Eucherius kept in touch with men renowned for learning and piety: John Cassian, Hilary of Arles, Saint Honoratus, later bishop of Arles, Claudianus Mamertus, Agroecius (who dedicated a book to him), Sidonius Apollinaris and his kinsman Valerian, to whom he wrote his Epistola paraenetica ad Valerianum cognatum, de contemptu mundi ("Epistle of exhortation to his kinsman Valerian, On the contempt of the world") an expression of the despair for the present and future of the world in its last throes shared by many educated men of Late Antiquity, with hope for a world to come: Erasmus thought so highly of its Latin style that he edited and published it at Basel (1520).
His Liber formularum spiritalis intelligentiae addressed to his son Veranius is a defence of the lawfulness of reading an allegorical sense in Scripture, bringing to bear the metaphors in Psalms and such phrases as "the hand of God." The term anagoge (ἀναγωγὴ) is employed for the application of Scripture to the heavenly Jerusalem to come, and there are other examples of what would become classic Medieval hermeneutics.
The fame of Eucherius was soon so widespread in southeastern Gaul that he was chosen bishop of Lyon. This was probably in 434; it is certain, at least that he attended the first Council of Orange (441) as Metropolitan of Lyon, and that he retained this dignity until his death. He was succeeded in the bishopric by his son Veranius, while his other son, Salonius, became Bishop of Geneva.
Among Eucherius' other letters are his Institutiones ad Salonium addressed to his other son. Many homilies and other writings have been attributed to Eucherius.