The first documented bishop of Cattaro was Paulus, who participated in the Council of Chalcedon in 451. The next mention of the Diocese of Cattaro was 530, when it is mentioned as a suffragan of the Archdiocese of Salona. The late Antiquity era, relatively the early Christian origin of the bishopric of Cattaro, is testified by an early Christian baptistery from the late 5th or early 6th centuries, discovered in an archeological examination of the Church of Saint Maria of Rijeka following the 1979 earthquake where the probable foundations of the first cathedral in Cattaro was discovered with remains, such as the cathedra and ciborium from the 6th century. John, a bishop of Cattaro, was certainly mentioned in the acts of the Second Council of Nicaea in 787. John was also mentioned in 809 in epigraphical inscriptions found in Cattaro. Bishops of Cattaro were mentioned in Ecclesiastical Assembly of Spalatum in 925 and 928, during the reign of King Tomislav. Only a fragmental list of the bishops before the 11th century were preserved. Afterward, since 1090 till the present day, a complete list has existed, beginning with bishop Grimoald, of Lombard origin. A Pontifical and Lectionary of the Bishopric is kept in Saint Petersburg. This artifact testifies that Cattaro remained under the jurisdiction of the Western Church following the Great Schism of 1054. In 1025, Pope John XIX issued a papal bull in which Cattaro became a suffragan of the Diocese of Canusium. In 1063, Pope Alexander II issued a papal bull in which Cattaro is also mentioned as a suffragan of the Archdiocese of Barium, previously known as the Diocese of Canusium. In 1067, the diocese became subjected to the Archdiocese of Dioclea-Antivari. Then, in 1078, the diocese became subjected to the Archdiocese of Ragusa, only to be returned under the control of Antivari in 1089. In 1120, the diocese of Cattaro was returned under the control of Dubrovnik. Between 1172 and 1828, the diocese was under the control of the Archdiocese of Barium. From 1828 to 1932, the diocese became a suffragan of the Archdiocese of Zadar. From 1932 to 1969, it became directly subjected to the Holy See. However, from 1969, the diocese of Cattaro has been a suffragan of the Archdiocese of Split-Makarska. Between the 13th and 14th centuries, the borders of the diocese reached the Danube. Under the diocesan jurisdiction were: Prizren, Janjevo, Novo Brdo, Novi Pazar, Brskovo, Golubac, Brvenik, Plana, Mačva, Trepča, Trgovište and Belgrade. In the 16th century, Tripo Bisanti, Bishop of Cattaro, signed himself as the Bishop of Serbia. In 1880, the parishes of Spič, Šušanj and Brca, which had originally belonged to the Archdiocese of Antivari, was transferred to the Diocese of Cattaro by the decision of the Sacred Congregation for the Propagation of the Faith. The first patron of the diocese was Saint George, who was later replaced by Saint Tryphon, whose relics were brought to Cattaro on 13 January 809. A church dedicated to Saint Tryphon was built in the early 9th century by Andrea Saracenis, a citizen of Cattaro.
