The first part of the name derives from the Latin "Romana Mansio", having been in the past a Roman "mansio" (coach station), whilst the second part "Sesia", derives from the name of the river that runs through the area. It is a municipality in the province of Novara on the border with the territory of Vercelli: the river Sesia, which creates extremely picturesque views, marks the border with the neighboring municipalities.
The discovery of archaeological finds of Roman origin confirm that Romagnano was a Roman "mansion" site already in the I century A.D. The history of the town in subsequent periods is supported by historical documents: the first, dating from 882, testifies its membership in the Marca of Ivrea and its sale to the Bishop of Vercelli. Later records report the presence in year 1000 of an ancient Benedictine abbey, which has great significance for the development of the area.
In the XII century it became a fief including other the towns of Prato and Cavallirio. During the XIII century the Castro Breclema, until that time domain of the Counts of Briand, was destroyed and its territory was incorporated into that of Romagnano. It was feud of the Marquis of Romagnano first and, with the decline of this, it was ceded to the Dal Pozzo, the Borromeo and the Ferrero, finally the Visconti. In the course of a clash between the French and Spanish in 1524, the famous knight Pierrre Terrail, known as the Bayard, was mortally wounded near Romagnano. Officially the town acquired the status of an autonomous municipality in 1600 thanks to the Duke of Milan Filippo III. In the XVI century it became the dominion of the Duchy of Milan under the Counts of Savoy and of Serbelloni till 1734. In 1787, abolished the feudal estates, it became autonomous and in the XIX century the traditional agriculture vocation practiced in the territory was gradually replaced by an industrial one.

Not to miss:

- the Parish of the Holy Annunciation and St. Silvanus the present structure features the refurbishment of 1856, the last of others made on the ancient pre-existing structure. Inside the building preserves a table attributed to Alba Macrinus and paintings of Lanino.
- the cellar of the Saints is the only remain of architectural elements of an ancient Benedictine abbey rich. In the vault are preserved frescoes depicting Saul and King David, dating back to mid-V century.
- the Church of Santa Maria del Popolo built in the first half of the XVII century on an existing building, later enlarged. The dome was frescoed by the painter Tarquinio Grassi between the XVII and XVIII centuries.
- the Praetorian Tower that belonged to the ancient Praetorian Palace, was raised in the second half of the XV century. It features a rectangular plan.
- the Oratory of San Martino of Breclema in Romanesque style, dating back to the XI century.
- the bridge over the river Sesia of medieval origin.
- the Ethnographic museum of history of Lower Valsesia on Mount Cucco. It seats in Villa Caccia, a hunting residence of the counts, built at the end of the first half of the XIX century. It presents a beautiful façade topped by a pediment and decorated by a double row of columns.