Roman Catholic Diocese of Porto Portugal Tags: Clerical Administrative Region, Diocese.The Portuguese Roman Catholic diocese of Porto (Latin: Dioecesis Portugallensis) (Oporto) is a suffragan of the archdiocese of Braga. Its see at Porto is in the Norte region and the second largest city in Portugal. thumbnail area (km2) 3.01e+09 country Portugal Established 588 patron Assumption of Mary province Roman Catholic Archdiocese of Braga Learn more... Loading...