| Province of Viterbo | |
| Native Name Lang: | it |
| Settlement Type: | Province |
| Image Alt: | Viterbo, the Palace of the Popes |
| Map Alt: | Map with the province of Viterbo in Italy |
| Subdivision Type: | Country |
| Subdivision Name: |  Italy |
| Subdivision Type1: | Region |
| Subdivision Name1: | Lazio |
| Seat Type: | Capital |
| Seat: | Viterbo |
| Parts Type: | Comuni |
| Parts Style: | para |
| P1: | 60 |
| Leader Party: | FI |
| Leader Title: | President |
| Leader Name: | Alessandro Romoli |
| Unit Pref: | Metric |
| Area Footnotes: | [1] |
| Area Total Km2: | 3615.24 |
| Population Footnotes: | [2] |
| Population Total: | 318163 |
| Population As Of: | 30 April 2017 |
| Population Density Km2: | auto |
| Demographics Type2: | GDP |
| Demographics2 Footnotes: | [3] |
| Demographics2 Title1: | Total |
| Demographics2 Info1: | €6.559 billion (2015) |
| Demographics2 Title2: | Per capita |
| Demographics2 Info2: | €20,425 (2015) |
| Timezone1: | CET |
| Utc Offset1: | +1 |
| Timezone1 Dst: | CEST |
| Utc Offset1 Dst: | +2 |
| Postal Code Type: | Postal code |
| Postal Code: | 01100, 010xx |
| Area Code Type: | Telephone prefix |
| Area Code: | 0761, 0763, 0766, 06 |
| Registration Plate: | VT |
| Blank Name Sec1: | ISTAT |
| Blank Info Sec1: | 056 |
| Website: | Official website |
The province of Viterbo (Italian: provincia di Viterbo) is a province in the Lazio region of Italy. Its capital is the city of Viterbo.
Viterbo is the most northerly of the provinces of Lazio. It is bordered to the south by the Metropolitan City of Rome Capital and to the south-east by the province of Rieti. It is also bordered by the regions of Tuscany (province of Grosseto) to the north and by Umbria (province of Terni) to the east. The Tyrrhenian Sea is located to the west.[4]
The territory falls in and makes up the largest part of the historical region of Tuscia, with the name sometimes being used synonymously with that of the province.
As of 2017, the province has a total population of 318,163 inhabitants over an area of 3615.24km2, giving it a population density of 89.05 inhabitants per square kilometre. The provincial president is Marcello Meroi and the province contains 60 Italian: [[comune|comuni]] (municipalities).[5]
The territory of the Province of Viterbo can be roughly divided into four geographical areas:
It can be said that the city of Viterbo geographically belongs both to the Alta Tuscia and the Cimini area, as it is located right below the mountains, yet at a short distance from Lake Bolsena.
The area of the province of Viterbo contained a number of Etruscan cities including Tuscania, Vetralla, Tarquinia, and Viterbo.[6] Viterbo was conquered by the Roman Republic in 310 BCE; despite this, minimal information is known of the city until it was utilised in 773 CE by Desiderius, King of the Lombards, as a base against the Holy Roman Empire. Matilda of Tuscany gifted the city to the papacy in the 11th century. Frederick Barbarossa was based in Viterbo as he planned to invade Rome in 1153, and he conquered the city in 1160 while preparing to attack Rome.[6]
After a period as a free commune, in the early 13th century Viterbo became part of the Papal States.[6] The Knights of Saint John were expelled from Rhodes in the 16th century and were temporarily granted refuge in Viterbo before they could travel to Malta. Pope Paul III described himself as a citizen of Viterbo and formed a university in the city. It joined the Kingdom of Italy on 12 September 1870 and during World War II, Viterbo was heavily bombed.[6]