The Diocese of San Marino-Montefeltro was until 1977 the historic diocese of Montefeltro. It is a suffragan of the metropolitan Archdiocese of Ravenna-Cervia. The diocese includes all the parishes of San Marino. The earliest mention of Montefeltro, as ''Mona Feretri'', is in the diplomas by which Charlemagne confirmed the donation of Pepin. The first known bishop of Montefeltro was Agatho (826), whose residence was at San Leo. Under Bishop Flaminios Dondi (1724) the see was again transferred to San Leo, but later it returned to Pennabilli. The historic diocese was a suffragan of the archdiocese of Urbino. Since 1988, there is formally an apostolic nunciature to the republic, but it is vested in the nuncio to Italy.