Naples Cathedral, or the Cathedral of the Assumption of Mary, is a Roman Catholic cathedral, the main church of Naples, southern Italy, and the seat of the Archbishop of Naples. It is widely known as the Cathedral of Saint Januarius, in honour of the city's patron saint.

Naples is the regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 909,048 within the city's administrative limits as of 2022. Its province-level municipality is the third-most populous metropolitan city in Italy with a population of 3,115,320 residents, and its metropolitan area stretches beyond the boundaries of the city wall for approximately 30 kilometres.