Nonio is a comune (municipality) in the Province of Verbano-Cusio-Ossola in the Italian region Piedmont, located about 100 kilometres (62 mi) northeast of Turin and about 15 kilometres (9 mi) southwest of Verbania.

Nonio borders the following municipalities: Cesara, Omegna, Pella, Pettenasco, Quarna Sotto, Varallo.