Romagnano Sesia is a town and comune (municipality) of about 4,000 inhabitants in the Province of Novara in the Italian region Piedmont, located about 80 kilometres (50 mi) northeast of Turin and about 25 kilometres (16 mi) northwest of Novara.

Romagnano Sesia borders the following municipalities: Cavallirio, Fontaneto d'Agogna, Gattinara, Ghemme, Prato Sesia, and Serravalle Sesia. Sights include the so-called "Cantina dei Santi" (Saints' cellar), which is a room which is the only remaining evidence of the ancient, powerful Benedictine monastery of S. Silano. The Cantina is completely painted with frescos dating back to the 15th century (Biblical story of David and King Saul).

The town already existed in the 1st century AD, when it constituted a path that connected the Novara area with Valsesia; its name derives from "Romana Mansio". Archaeological finds from the Roman era discovered during excavations testify to this ancient origin.