Vallanzengo is a comune (municipality) in the Province of Biella in the Italian region Piedmont, located about 70 kilometres (43 mi) northeast of Turin and about 4 kilometres (2 mi) northwest of Biella. As of 31 December 2004, it had a population of 236 and an area of 3.9 square kilometres (1.5 sq mi).

Vallanzengo borders the following municipalities: Bioglio, Callabiana, Camandona, Mosso, Piatto, Quaregna, Trivero, Valle Mosso, Valle San Nicolao.