The Diocese of Bergamo (Latin: Dioecesis Bergomensis; Italian: Diocesi di Bergamo; Lombard: Diocesi de Bergum) is a Latin diocese of the Catholic Church in Italy, and is a suffragan of the Archdiocese of Milan. Geographically, Bergamo stood between the mainland interests of the Republic of Venice, and the territory of the Duchy of Milan. The duchy was regularly contested by the French and the Holy Roman Empire, which brought about repeated military operations. Internally, from the 12th to the 15th century, there was the usual party strife between the Guelphs, who generally supported the political and religious policies of the Papacy; and the Ghibellines, who generally supported the Emperors. As Kings of Italy, the emperors were feudal overlords of Lombardy.
The diocese was founded in the fourth century AD. Its first bishop was Narno, who was succeeded by Viator.