The Diocese of Guastalla (Dioecesis Guastallensis) was a Catholic suffragan bishopric in the province of Reggio Emilia, Italy, from 1828 to 1986. It began as a small chapel, ordered by a Holy Roman Emperor in 865; it was promoted into being a parish; it then became a territorial abbey; and finally, after the Napoleonic occupation of Italy, it was made a diocese at the request of his second wife. The diocese employed the Roman rite.[1][2]