According to the Greek historian Dionysius of Halicarnassus, Celleno was founded by “Italo descendant of Oenotrus, in memory of his daughter Cilenia; many years before the siege of Troy.” In Greek mythology, Celeno was one of the three harpy (female monster in the form of a bird with a human face) daughters of Thaumas and Electra.
From the discovery of archaeological remains, Celleno was formed around the seventh century BC and was quite important during the Etruscan era due to its location on the road linking Orvieto to Ferento.
The advantages and disadvantages this strategic location brought meant that it was conquered by the Romans in 264 BC who were interested to control its connections to Viterbo and there was a subsequent period of calm. With the end of the Roman Empire, along the trade routes came the invaders and Celleno suffered continuous sieges and pillage by the Goths, Lombards and Byzantines.
Finally in 774 Charlemagne drove the Lombards out and handed Celleno, along with other estates, to the Church. It was entrusted by the Apostolic Camera to the family of Monaldeschi who were engaged for a long time in the continuous struggles between the Guelphs and Ghibellines, between Viterbo and Orvieto.
In the twelfth century it was removed from control by Viterbo, which had lent aid in 1172 against Ferento. But in 1316 it was again attacked and plundered by the troops of Orvieto led by Poncello Orsini. In 1329 it passed to Orvieto and only to return to Viterbo in 1392 to guarantee the loyalty commitments from Orvieto towards the Holy See.
The fiefdom was assigned to the Viterbo family of the Alessandri and, in 1396, Boniface IX gave it in perpetual curacy to Sylvestro Gatti, with the payment of annual a pound of wrought silver. When the Gatti family became extinct, with the killing of Giovanni Gatti who had refused obedience to the pope, the fiefdom was assigned in 1527 by Pope Clement VIII to Franciotto Orsini.
Celleno remained with the Orsini until 1580 when it came under the control of the Apostolic Camera.
The old town centre was almost abandoned in the subsequent years due to several earthquakes from that of 1695 to the most destructive of 1855. So, from the end of the nineteenth century a new settlement was formed in another place and the old town emptied but the centre is not completely abandoned.