The Diocese of Comacchio (Latin: Dioecesis Comaclensis) was a Roman Catholic diocese located in the coastal town of Comacchio in the province of Ferrara and region of Emilia Romagna, Italy. In 1986, the diocese of Commachio was united with the diocese of Ferrara to form the Roman Catholic Archdiocese of Ferrara-Comacchio, and lost its individual identity.