It had been created from the diocese of Valence. There had been a previous diocese of Die, up to the thirteenth century.
The Carthusian Polycarpe de la Riviere gives a St. Martinus (220) as first Bishop of Die. The oldest historically known bishop, St. Nicasius, attended the First Council of Nicaea in 325. After him are mentioned: St. Petronius, followed by his brother St. Marcellus (c. 463), confessor and miracle-worker; Lucretius (541-73), to whom St. Ferreolus of Uzes dedicated his monastic rule. For various reasons Abbé Jules Chevalier omits from the episcopal list: St. Maximus (sixth century); Wulphinus (end of eighth century); Exuperius and Saturninus (ninth century). Other bishops were: Hugh (1073-83), consecrated at Rome by Gregory VII, became a papal legate of the latter, presided over numerous councils for the reform of the Church, and subsequently became Bishop of Lyon; St. Ismido (1098-1115) of the noble house of Sassenage; Blessed Uric (1129-42), who opposed the Petrobrusian heresy in his diocese and became a Carthusian; Blessed Bernard (1173-76); St. Stephen (1203-8), formerly a Carthusian at the monastery of Portes; Blessed Didier (Desiderius) de Lans (1213-20).
After the eleventh century the Diocese of Die, long disputed between the metropolitans of Vienne and Arles, became suffragan of the archbishopric of Vienne. By Papal Bull of 25 September, 1275, in order to strengthen the Church of Valence in its struggle with the House of Poitiers, Gregory X united the Diocese of Die with that of Valence. This union, which lasted four centuries, was unfortunate for Die. It was annulled in 1687 by king Louis XIV, who, to combat Protestantism, appointed a Bishop of Die.