Pettenasco is a comune in the Province of Novara in the Italian region of Piedmont, located about 100 kilometres northeast of Turin and about 40 kilometres 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 7.1 square kilometres.
The municipality of Pettenasco contains the frazioni 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.