After the French Concordat of 1801, the diocese became a suffragan of the Archdiocese of Aix-en-Provence and Arles,[3] until 2002 when it was attached to the archdiocesan province of Marseille.

[6] In 1759, Ajaccio had a population of around 5,000, under the political control of the Republic of Genoa, though the diocese was suffragan to the Metropolitan Archdiocese of Pisa.

[9] There is a legend that the bishops banished from Africa to Corsica in 484 by Hunneric, Arian King of the Vandals, built with their own hands the primitive cathedral of Ajaccio.

The present cathedral, dating from 1554 to 1593, owes its construction to the initiative of Gregory XIII, who while still Ugo Buoncompagni, spent some time at Ajaccio as papal legate.

It is said that the cathedral was designed by Giacomo della Porta, but a guidebook remarks, "Se è vero, non era molto in forma.