Oleggio is a comune (municipality) in the Province of Novara in the Italian region Piedmont , located about 90 kilometres (56 mi) northeast of Turin and about 15 kilometres (9 mi) north of Novara. As of 31 December 2004, it had a population of 12,490 and an area of 37.8 square kilometres (14.6 sq mi).

Among its churches is the 10th-century, Romanesque-style San Michele.

Oleggio borders the following municipalities: Bellinzago Novarese , Marano Ticino , Mezzomerico , Momo, Vaprio d'Agogna, and Vizzola Ticino.