Around the start of the first millennium the Osco-Umbrians, a people with a language of Indo-European origin that dominated the left bank of the Tiber that vertically cuts the region to the Adriatic Sea, settled in the area and called the town Nequinum.

The Romans conquered Nequinum in the 4th century BC and made it a position of force at a key point of the Via Flaminia, the famous road which connected the city of Rome to the Adriatic Sea (at that time the road passed through the town descending to the right bank of the Nera to then carrying on to Carsulae, Acquasparta, Massa Martana and Spoleto).

The rediscovery, in the late 20th – early 21st century, of an ancient Roman shipyard within its territory has made researchers hypothesise its particular importance during the Punic Wars.

I have spoken, I think, of Roman provinces, and yet I have not said their gods are Roman for they are not worshipped at Rome any more than others who are ranked as deities over Italy itself by municipal consecration, such as Delventinus of Casinum, Visidianus of Narnia, Ancharia of Asculum, Nortia of Volsinii, Valentia of Ocriculum, Hostia of Satrium, Father Curls of Falisci, in honour of whom, too, Juno got her surname.

From the 11th century it began to increase in wealth and power, was opposed to Pope Paschal II in 1112 and rose against Barbarossa in 1167.

This insubordination cost Narni a ferocious repression imposed by the archbishop Christian of Mainz, Barbarossa's chancellor.

A decisive turning-point in Narni's history was reached on 15 July 1527[10] The troops of Charles V, mostly in fact German mercenaries (Landsknechts), put the city to fire and sword; it lost its ancient prosperity.

Even the inhabitants of Terni took advantage of the situation to deliver their blame to give vent to their long-repressed hatred of Narni.

Like many of the smaller towns of Umbria, Narni is still of strikingly medieval appearance today, with stone buildings, and narrow cobblestone streets.

The town is famous for one of the largest Roman bridges (Ponte d'Augusto)[11] ever built, by which the Via Flaminia crossed the Nera.