It is bordered to the north with the Province of Perugia, to the east, south and west with the Lazio (Province of Rieti and Province of Viterbo) and to north-west with the Tuscany (Province of Siena).
The province of Terni is characterized by its slopes encountered along the path of rivers, allowing the exploitation of hydro catchment areas, so as to have led to the creation of several artificial lakes: .