Pettenasco is a comune (municipality) in the Province of Novara in the Italian region of Piedmont, located about northeast of Turin and about northwest of Novara. It lies on the eastern shore of Lake Orta.
As of 31 December 2004, it had a population of 1,318 and an area of .
The municipality of Pettenasco contains the frazioni (subdivisions, mainly villages and hamlets) Pratolungo, Crabbia, and Poggio Luneglio. A daily ferry service connects Pettenasco with Omegna and towns and villages around the lake.
Pettenasco borders the following municipalities: Armeno, Miasino, Omegna and Orta San Giulio.