The diocese of Marsico Nuovo was a Roman Catholic ecclesiastical territory in Basilicata, southern Italy, which existed until 1818. It was a suffragan of the archbishops of Salerno. In 1818, Marsico Nuovo was united aeque principaliter with the diocese of Potenza, to form the diocese of Marsico Nuovo and Potenza.
Marsico Nuovo is a city of the province of Potenza in Southern Italy. Its origin is obscure, but the ancient Grumentum was destroyed by the Saracens.
It is said that a Saint Laberius or Saverius first preached the Gospel there. In the story of Laberius appears the name of a Bishop Sempronius Atto; both are inventions. An attested bishop of Grumentum is Tullianus (c. 558-560). In a letter of July 599, Pope Gregory I orders Romanus, his Defensor Siciliae, to intervene in a squabble between two men "in parochia Grumentina."
The town of Marsico Nuovo grew in importance, and became under the Normans the seat of a county. It became an episcopal see, dioecesis Marsicensis, when a bishop of Grumentum established his residence there, retaining, however, his former title. A number of bishops had formerly been assigned to Marsico Nuovo in the Lombard period who actually belonged to the diocese of the Marsi; the confusion persists even beyond that period.
Marsico Nuovo appears as a diocese in a papal document of 24 March 1058, in which Pope Stephen IX confirmed the diocese of Salerno in its archiepiscopal and metropolitan status. He listed the suffragan dioceses assigned to Salerno, including Marsico.
In 1744, the city of Marsico Nuovo had a population of c. 4,000 persons. In addition to the cathedral, there were four parish churches, two religious houses of men, and one of women. The monastery of S. Stephen Protomartyr had been founded inside the city; the monastery of S. Peter Tramutulae had been founded in 1150 by the monk Giovanni from the monastery of Cava (who later became Bishop of Marsico); and the monastery of S. Thomas of Canterbury at Raya had been founded by Count William of the Marsi in 1179.
On 27 June 1818, the diocese of Potenza was united with the Diocese of Marsico Nuovo aeque principaliter, to form Diocese of Potenza e Marsico Nuovo. Potenza was made a suffragan of the archdiocese of Acerenza, along with Anglona e Tursi, Tricarico, and Venosa.
Following the Second Vatican Council, and in accordance with the norms laid out in the council's decree, Christus Dominus chapter 40, Pope Paul VI ordered a reorganization of the ecclesiastical provinces in southern Italy. The decree "Eo quod spirituales" of 12 September 1976 created a new episcopal conference in the region called "Basilicata", to which were assigned all of the dioceses that belonged to the ecclesiastical province of Potenza, including Materana and Mons Pelusii; they had formerly belonged to the episcopal conference of "Apulia". Pope Paul VI ordered consultations among the members of the Congregation of Bishops in the Vatican Curia, the Italian Bishops Conference, and the various dioceses concerned. After twenty years, problems and objections were still apparent.
On 18 February 1984, the Vatican and the Italian State signed a new and revised concordat. Based on the revisions, a set of Normae was issued on 15 November 1984, which was accompanied in the next year, on 3 June 1985, by enabling legislation. According to the agreement, the practice of having one bishop govern two separate dioceses at the same time, aeque personaliter, was abolished. The Vatican continued consultations which had begun under Pope John XXIII for the merging of small dioceses, especially those with personnel and financial problems, into one combined diocese.
On 30 September 1986, Pope John Paul II ordered that the dioceses of Potenza, Marsico Nuovo, and Muro Lucano be merged into one diocese with one bishop, with the Latin title Archidioecesis Potentina-Murana-Marsicensis. The seat of the diocese was to be in Potenza, and the cathedral of Potenza was to serve as the cathedral of the merged diocese. The cathedrals in Marsico Nuovo and Muro Lucano were to become co-cathedrals, and their cathedral Chapters were each to be a Capitulum Concathedralis. There was to be only one diocesan Tribunal, in Potenza, and likewise one seminary, one College of Consultors, and one Priests' Council. The territory of the new diocese was to include the territory of the suppressed dioceses of Marsico Nuovo and Muro Lucano.
27 June 1818: United with the Diocese of Potenza to form the Diocese of Potenza e Marsico Nuovo