The Roman Catholic Diocese of Civita Castellana is a diocese located in the region of Lazio, Italy. It was established in the 4th century and is part of the ecclesiastical province of the Archdiocese of Rome. The diocese covers several towns, including Civita Castellana, and serves the spiritual needs of its Catholic population through various parishes and institutions. The diocese is known for its rich history and cultural heritage, featuring notable churches and religious sites. The Cathedral of Santa Maria Maggiore serves as the diocese's main church, reflecting the architectural styles and traditions of the region.