The Archdiocese of Agaña is a Latin Church ecclesiastical territory or diocese. It comprises the United States dependency of Guam. The prelate is an archbishop whose cathedral is the Dulce Nombre de Maria Cathedral-Basilica.

Diego Luis de San Vitores, SJ was a Spanish Jesuit missionary who founded the first Catholic church on the island of Guam. He is responsible for establishing the Christian presence in the Mariana Islands. He is a controversial figure in some circles due to his role in the Spanish–Chamorro Wars.