Castelverrino is a comune, or municipality, situated in the Province of Isernia within the Italian region of Molise. It is located in the interior of the peninsula, positioned approximately 30 kilometres (19 mi) northwest of Campobasso and about 25 kilometres (16 mi) northeast of Isernia.
The town serves as a local administrative center within its province. Its geographical location places it in the heart of the Molise region, characterized by its proximity to these two major regional hubs.