Onano is located in the mountains on the border between Lazio and Tuscany, near Lake Bolsena, in an area populated since Etruscan times.
The first traces of the village date back to the Middle Ages. As a result its strategic position, Onano was involved in resolution of the conflict between Guelphs and Ghibellines.
Onano was controlled by the Monaldeschi family and then the Sforza who also obtained the title of Duke of Onano. In the seventeenth century, Onano came back under the direct control of the Church and was a summer residence of Pope Pius XII Pacelli.