| Cattedrale di San Pietro Apostolo | |
| Native Name Lang: | Italian |
| Religious Affiliation: | Roman Catholic |
| Architecture Type: | Church |
| Location: | Isernia Molise |
| Map Type: | Italy Molise#Italy |
Isernia Cathedral (Italian: Duomo di Isernia, Cattedrale di San Pietro Apostolo) is a Roman Catholic cathedral in the city of Isernia, Italy, the seat of the Bishop of Isernia-Venafro. It is dedicated to the Apostle Peter. The cathedral is situated in the Piazza Andrea in the old town of Isernia, and stands on the site of an Italic pagan temple of the 3rd century B.C. Construction of the present building began in 1349. Its present appearance is the result of many renovations, occasioned partly by numerous earthquakes and partly by building refurbishments.