The presence of ancient settlement in the area has been proved by excavations held in the frazione of Cireggio, archaeological findings dating from the late Bronze and Iron Ages. Omegna is mentioned in 1221 AD, when the population gave itself to the commune of Novara.
In the 19th and early 20th century it became an industrial center (it was for many years the main centre for production of pots and small home appliances in Italy) and the population was increased by immigrants. In 1913 Omegna was connected with Pallanza by an electrical tramway line. It was declared a city in 1939. During World War II it was a center of partisan resistance against the German-Fascist occupation.
Church of Sant'Ambrogio. It is a late-Romanesque building with a nave and two aisles, with side chapels. The bell tower is still mostly the medieval one. The interior is now in Baroque style, and houses an altarpiece by Fermo Stella da Caravaggio (1547) and an urn with the relics of St. Vith, patron saint of Omegna.
Ponte Antico ("Ancient Bridge", 15th century), over the Strona river.
Porta della Valle ("Valley Gate", c. 1100 AD), also known as Porta Romana. It is the only surviving one among the five medieval gates of Omegna.