Poggio Sannita is a comune located in the Province of Isernia within the Molise region of Italy. It is situated approximately 30 kilometres northwest of Campobasso and about 25 kilometres northeast of Isernia.
The municipality sits on a promontory surrounded by the Verrino and Sente rivers. Both rivers are primarily torrential in nature, with the Sente river drying up completely during the summer months.