The tradition wants Valentano to derive from the etrusca “Verentum” but traces could not be found. Only for the Roman period well visible are the rests of numerous villas scattered along a byway of the Street Clodia. Rustic villas, in the log run turned themselves in small villages that, in medieval epoch for the sake of defense felt the necessity to reunite together, on the top of the hill where, the first nucleus of that called village was probably formed “Valentano” (perhaps in Valley of the Ontanis). longobardes are present also rests of fortifications with necropolis toward the place “La Fortezza”.
The first news of the country could be those of 680, when the bishop of the destroyed city of Bisenzo would move for brief time in this center. From the documents of the imperial Abbeys of Farfa and St. Savior on the Amiata Mountain we know about the first certain documents of the country dated in the years 813-844.
In the year 844, in documents of the Imperial abbey of S. Salvatore on the Amiata Mountain (IX century) is mentioned Balentanu or Valentano.
In 1053 however the village is already structured and it appears organized as free commune, in the location currently used, with its parish devoted to St. John the Evangelist and the Fortress of defense. From this period and actually to halves of the XIV century, the country knew destructions, fires, devastations and reconstructions, and was contended by the dominion of the near cities of Orvieto and Viterbo.
In 1354 the town, recovered by the cardinal Albornoz, was assigned to the dominion of the Farneses for long years, turning into the residential building of the Family, the ancient fortress of defense, with Renaissance courtyard and great hall and also asking for the artistic intervention of Antonio da Sangallo il Giovane.