Ternengo is a comune (municipality) in the Province of Biella in the Italian region Piedmont, located about 60 kilometres (37 mi) northeast of Turin and about 3 kilometres (2 mi) southeast of Biella. As of 31 December 2004, it had a population of 310 and an area of 2.0 square kilometres (0.77 sq mi).

Ternengo borders the following municipalities: Bioglio, Pettinengo, Piatto, Ronco Biellese, Valdengo.