Teano is a town and comune in the province of Caserta, Campania, southern Italy, 30 kilometres (19 mi) northwest of Caserta on the main line to Rome from Naples. It stands at the southeast foot of an extinct volcano, Rocca Monfina. Its St. Clement's cathedral is the see of the Roman Catholic Diocese of Teano-Calvi, which started as the Diocese of Teano circa AD 300.