The Diocese of Terni-Narni-Amelia is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Umbria, central Italy. It was created in 1983, when the Diocese of Amelia was united with the Diocese of Terni and Narni. The latter had been in turn created in 1907, when the Diocese of Narni was united to the historical Diocese of Terni. The diocese is immediately exempt to the Holy See, not part of any ecclesiastical province.

The Italian Catholic diocese of Narni, in central Italy, was suppressed in 1907, becoming part of the diocese of Terni.