Catholic Church in Croatia
The Catholic Church in Croatia is part of the worldwide Catholic Church that is under the spiritual leadership of the Pope. The Latin Church in Croatia is administered by the Croatian Bishops' Conference centered in Zagreb, and it comprises five archdioceses, 13 dioceses and one military ordinariate. Dražen Kutleša is the Archbishop of Zagreb.
A 2011 census estimated that there were 3.7 million baptized Latin Catholics and about 20,000 baptized Eastern Catholics of the Greek Catholic Church of Croatia and Serbia in Croatia, comprising 86.3% of the population., weekly church attendance was relatively high compared to other Catholic nations in Europe, at around 27%. A 2021 Croatian census showed that 83% of the population is Catholic and 3.3% is Serbian Orthodox.
The national Marian shrine of Croatia is in Marija Bistrica, while the country's patron is Saint Joseph: the Croatian Parliament unanimously declared him to be the national patron in 1687.
History
Roman Illyrians and early Christianity
The western part of the Balkan Peninsula was conquered by the Roman Empire by 168 BC after a long drawn out process known as the Illyrian Wars.Following their conquests, the Romans organised the area into the province of Illyricum, which was eventually split up into Dalmatia and Pannonia. Through being part of the Roman Empire, various religious cults were brought into the region. This included the Levantine-originated religion of Christianity. Christianity became the official religion of the Roman Empire in 391. In 395, the Roman Empire was divided into two parts, and the dividing line went through the Balkans. Illyricum fell under the rule of Rome and the rest fell under the rule of Byzantium.
Indeed, Salona, the capital city of the province of Dalmatia, was one of the earliest places in the region connected with Christianity. It was able to gain influence first among some of the Dalmatian Jews living in the city. St. Titus, a disciple of St. Paul the Apostle and the subject of the Epistle to Titus in the New Testament, was active in Dalmatia. Indeed, in the Epistle to the Romans, Paul himself speaks of visiting "Illyricum", but he may have meant Illyria Graeca.
Conversion of the Croats
Somewhere in the early 7th century the Archdiocese of Salona vanished with the plundering raids of Sclaveni and Pannonian Avars, and Roman population found refuge in the Diocletian's Palace and other coastal cities and islands. Pope Gregory I in his letters wrote about the arrival of Slavs in Dalmatia and Istria. Soon the Holy See, which had jurisdiction and ecclesiastical order in the territory of former Diocese of Illyricum, began the process of Christianization.The Croats settled in the area of present-day Croatia after successful war against the Avars, liberating province of Dalmatia. Francis Dvornik considered that to the Croatian victorius advance is related account from Miracles of Saint Demetrius about the revolt and liberation of Christian hostages of the Avars between rivers Sava, Drava and Danube. The Croats had their first official contact with the Holy See in year 641 when the Pope John IV papal envoy led by Abbot Martin came to them to redeem Christian captives and the bones of the martyrs Anastasius, Maurus and Venancio. Such event "is witness to the civilised and peaceful co-existence established between the indigenous Christian population and the new rulers of what had once been Roman Dalmatia and Illyria".
There is little information about the "Baptism of the Croats", but it is known that it was peacefully and freely accepted, and that it started since the 7th century. Byzantine emperor Constantine Porphyrogenitus in his De Administrando Imperio wrote that the Heraclius, "obtained and brought priests from Rome and made of them an archbishop, bishop, presbyters and deacons, which then baptised the Croats". After the baptism, the Croats "made a convent, confirmed with their own signature, and by oaths sure and binding in the name of St. Peter the apostle, that never would they go upon a foreign country and make war upon it, but would rather live at peace with all who were willing to do so. They received from the same Pope of Rome this benediction: If some other foreigners should come against the country of these same Croats and bring war upon it, then might God fight for the Croats and protect them, and Peter the disciple of Christ give unto them victories". Nevertheless the exact dating of the convect agreement, it is again alluded in Pope John VIII's letters. Another possible evidence for Roman missionary work among the Croats in the 7th century would be letter of Pope Agatho in which are mentioned bishops active among Slavs. Thomas the Archdeacon in his early 13th century Historia Salonitana also mentioned Johannes de Ravenna, who was sent by the Pope in the mid-7th century to organize church life and restore Archdiocese of Salona, becoming in the process Archbishop of Split.
New population certainly did not completely convert at the time as initially probably encompassed only the Croatian elite members, neither such conversions are instantaneous events because missionary work seeks building a Christian mentality. The additional conversion stages were in the late 8th and early 9th century by Patriarchate of Aquileia and Prince-Archbishopric of Salzburg under Frankish supervision, and of pagan Narentines during the reign of Byzantine emperor Basil I.
Middle Ages
First certain signs of Church organization revival and active papal policy can be dated to the mid-or-late-8th century, with the Salonitan Archdiocese replaced as ecclesial centre by Roman Catholic Archdiocese of Zadar, and then by the Archbishopric of Spalathon by the late-8th century. The latter initially probably acted independently, without metropolitan bishop. Croatia after the Charlemagne's division of areas of Aquileia and Salzburg became under jurisdiction of the Patriarchate of Aquileia, and some Frankish priests are mentioned in historical sources. The activity of Lombard missionaires from Principality of Benevento could be argued on the appearance of St. Bartholomew the Apostle, while of Northern Italian missionaries the appearance of St. Ambrose, St. Martha and possibly St. Martin titulary.The Pax Nicephori between the Franks and Byzantium did not influence the ecclesial borders and jurisdiction of Croatia. By the mid-9th century, Croats have already been fully included in a large European Christian community. Croatian rulers Mislav, Trpimir I and many others were building churches and Benedictine monasteries. Pope Nicholas I warned the bishop and clergy of large Diocese of Nin that cannot establish new churches without papal approval, a reference to the foundation of the Diocese of Nin itself. Its formation was probably an act of Croatian dukes and local clergy to separate from Byzantine influence, because in the second half of the 9th century Byzantine emperor Basil I and Ecumenical Patriarch of Constantinople Photios I tried to expand on the already present Christian organization of the Roman Church in the region of former Praetorian prefecture of Illyricum, causing so-called Photian schism, managing to get control only of First Bulgarian Empire and Principality of Serbia. Before that, Constantinople Patriarchate did not have any jurisdictional pretensions over Western Illyricum. The presumed political alliance of duke Zdeslav with Byzantium some historians interpreted "as an ecclesiastical submission of Croatia to the Constantinople Patriarchate", but it is doubtful, as would certainly return under Roman Church jurisdiction during duke Branimir. However, the Holy See under Pope John VIII did not have complete power over the region of Croatia as would temporarily compete with Patriarch Valpert of the Patriarchate of Aquileia, but eventually in the 880s the bishop of Nin, Teodosius, got the papal pallium and temporarily until his death in 892 united the Diocese of Nin with Archdiocense of Split.
In 879, Croatian duke Branimir wrote a letter to Pope John VIII in which he promised him loyalty and obedience. Pope John VIII replied with a letter on 7 June 879, in which he wrote that he celebrated a Mass at the tomb of St Peter on which he invoked God's blessing on Branimir and his people, recognizing Duchy of Croatia as an independent and sovereign state. Both duke Trpimir and Branimir underdertook pilgrimages recorded in the Evangelistary of Cividale. Pope Leo VI while confirming the 2nd Church Council of Split mentioned that the Archbishop of Split was "in Croatorum terra". The church councils in 925 and 928 were held to discuss about the bishopric of Nin, which bishop Gregory of Nin called himself as "Episcopus Croatensis", and the usage of non-Latin liturgy.
Since the 9–10th century in Croatia existed a unique phenomenon in the entire world of Catholicism, a non-Latin liturgy that was held in Church Slavonic language with Glagolitic script by Cyril and Methodius, approved by Pope Adrian II and Pope John VIII. There's still scholarly debate whether Cyril and Methodius or their pupils visited Croatia until the end of the 9th century and whether the Glagolitic script also spread with direct Byantine mission in the mid-11th century. The brothers did not baptize the Croats as they were already baptized. In 1060/1061 the Pope Nicholas II declared "under the threat of excommunication forbade... to be ordained in Holy Orders if they have not learnt Latin", but Pope Gregory VII sent legate Girard under whom the "national synod of Dalmatian and Croatian bishops rehabilitated Glagolitism". Despite continued disputes in the usage of Slavic language in liturgy, as Glagolitians claimed that the script was created by St. Jerome and were adherents of the Catholic Church and canon law, the 13th century Pope Innocent IV again officially approved use of Church Slavonic language and the Glagolitic script to Filip bishop of Senj, thus making Croats the only Latin Catholics in the world allowed to use a language other than Latin in their liturgy prior to the Second Vatican Council in 1962. George of Slavonia in c. 1390 recorded that the "Croatian bishop knew both languages, Latin and Croatian, and was the first to celebrate mass sometimes in one and sometimes in the other language", called the Glagolitic script as "alphabetum chrawaticum", being used by the clergy in Istria and other eleven Croatian bishoprics. Glagolitians were supported by Croatian noble families, and Glagolitic script was used by several Catholic orders, Franciscans, but also Benedictine and Pauline Fathers, and later also Protestants in Istria.